volume	12,	no.	13 july	2012 Functionalism and the Metaphysics of Causal Exclusion David Yates Kings College, London © 2012 David	Yates This work is licensed under a Creative Commons Attribution-NonCommerical-NoDerivaties 3.0 License. <www.philosophersimprint.org/012013/> 1. Introduction Take functionalism to be the thesis that mental property M is the property of having some other property that plays a certain characteristic causal role	R.1 Functionalists are usually physicalists, and so take	mental properties to be physically realized, such that for any	mental property	M, there's a physical property P that fills R. Causal exclusion looms. Functionalism takes	mental properties to	be	characterised	by	causal	roles	that	are	filled	by	something	else. As M's realizer, P must do all the causal work (whatever that is) that	R involves, apparently leaving	nothing for	M to do. If	mental properties	are	causally	redundant,	and	if	causal	novelty	is	necessary for robust ontological commitment, then mental properties aren't really	real.2	This	would	be	no	small	irony	if	true,	because	historically, functionalism	was	motivated	by	the	need	to	explain	how	physically different	creatures	could	be	in	the	same	mental	state;	small	comfort to be told that it's by dint of falling under predicates that don't pick out genuine properties. Label properties that do causal	work "causally efficacious", setting aside for now the question of what causal work is. Those who argue that functionalism is consistent with	the	causal	efficacy	of	mental	properties	typically	adopt	one	of the	following	strategies:	(i)	deny	that	causal	novelty	is	necessary	for ontological commitment and argue that functional properties can inherit the efficacy of their realizers, resulting in a kind of causal over-determination;3 (ii) defend a difference-making theory of causation that entails that functional properties are causally novel after	all.4	Proponents	of	(i)	defend,	or	at	least	recognise	the	need	to defend,	theories	of	causation	that	vindicate	their	claim	that	functional properties inherit efficacy from their realizers. The task then is to argue	that	the	kind	of	over-determination	involved	isn't	problematic. 1. Functionalism	so	construed	isn't	limited	to	mental	properties.	My	arguments in	this	paper	depend	only	on	the	general	metaphysic	outlined	above. 2. Kim	(1992a,b,	1998).	I	will	fill	in	the	preceding	sketch	in	due	course. 3. Segal	and	Sober	(1992);	Bennett	(2003);	Witmer	(2003);	Kallestrup	(2006). 4. Yablo	(1992);	List	and	Menzies	(2009). ImprintPhilosophers' david	yates Functionalism and the Metaphysics of Causal Exclusion philosophers'	imprint – 2 – vol.	12,	no.	13	(july	2012) of	properties to	Section	3,	where I argue that the	mere fact that,	by Humean	lights,	a	property-instance	causes	some	effect,	doesn't	entail that	it's	an	instance	of	a	property	that	does	causal	work	in	relation	to that effect. Kim treats causation as a relation between fine-grained events,	construed	as	property-instances.	On	this	view	mental	events are numerically distinct from the physical events that realize them. Those who prefer coarse-grained events may recast the arguments that	follow	in	terms	of	single	events	having	both	mental	and	physical properties,	with	the	former	supervening	on	the	latter. 2.1 Kim's supervenience argument. The	most complete	presentation	of	Kim's supervenience argument occurs in	his	(2005).6	Kim	offers	two	versions	of the	argument; for brevity I focus on the simplest, which concludes that no property that's not identical to some physical property could cause an instance of a supervenient property. It's the supervenience of the effect property-instance on a physical base that drives the simple version	of	Kim's	argument.7	Kim	begins	by focusing	on "mental-tomental" causation,	which I take to involve instances	of intentional mental properties such as thirst causing instances of behavioural properties such as drinking. The argument also applies to causal chains of mental property-instances of the first kind; I focus on causation	of	behaviour	for	reasons	of	exposition.	Following	Kim,	let the	mental	property-instances	be	M	and	M*,	and let	M*'s	physical base property-instance be P*. For reductio, suppose that	M causes M*.	Kim	defends	a	principle	of	downwards	causation,	according	to which	the	only	way	to	cause	M*	is	to	cause	P*.	The	idea	is	that	since P*	realizes	M*,	to	suppose	an	event	could	cause	M*	without	causing P*	is	like	supposing	a	pill	could	alleviate	a	headache	without	causing any	brain	events. 6. ch.	2,	pp.	39–52. 7. The	more	complex	version	depends	on	the	supervenience	of	both	cause	and effect	properties. Proponents	of	(ii)	needn't	worry	about	over-determination,	because according to difference-making theories of causation, functional properties	make	a	difference	their	realizers	don't. Both strategies suffer, I argue, from	a failure to properly analyse the	notion	of	causal	work	as	applied	to	properties.	If,	as	is	commonly supposed, the causal work of a property consists in grounding the dispositions of its bearers, then the nature of functional properties renders it impossible for them to	do the same causal	work as their realizers. For related reasons, I argue, whatever the merits of the difference-making	account	of	causation,	it	can't	be	an	account	of	the causal	work that	properties	do.	Clarification	of the	notion	of causal work reveals a novel solution to the exclusion problem based on the relations between dispositional properties at different levels of mechanism,	which	involves	three	central	claims:	(i)	the	causal	work	of properties	consists	in	grounding	dispositions,	(ii)	functional	properties are	dispositions,	and	(iii)	the	dispositions	of	mechanisms	are	grounded in the dispositions of their components. Treating functional	mental properties	as	dispositions	of	components	in	psychological	mechanisms, I	argue that such	properties	do the	causal	work	of	grounding	agentlevel dispositions.	These	dispositions,	while	ultimately grounded in the	physical	realizers	of	mental	properties,	are	indirectly	so	grounded, through	a	hierarchy	of	grounding	relations	that	extends	upwards,	of necessity,	through	the	mental	domain. 2. The Causal Exclusion Problem and the Humean Backlash Proponents	of	Humean	approaches	to	causal	exclusion	suppose	that	the causal	efficacy	of	properties	can	be	captured	by	counterfactual	or	nomic relations	between	events,	typically	-	but	not	necessarily	-	construed as instances of the target properties. In Section 2.1, I discuss Kim's "supervenience	argument" against	mental causation,5 and in	Section 2.2,	I	show	how	the	Humean	strategies	outlined	above	are	supposed to block that argument. I postpone discussion of the causal work 5. Kim	(1998),	ch.	2;	(2005)	ch.	2. david	yates Functionalism and the Metaphysics of Causal Exclusion philosophers'	imprint – 3 – vol.	12,	no.	13	(july	2012) of the other.	As he notes, that doesn't seem to be the right	way to describe	the	way	in	which	-	putatively	-	M	and	P	both	cause	P*.12	In cases such as execution	by	firing squad, the	bullets of the	different marksmen over-determine the victim's death by causing instances of	distinct	properties in the	victim.	The	manner	of the	victim's	death is	altered by its being over-determined in this	way. This isn't to say that the victim	dies a different death by virtue of this kind of overdetermination	-	as Lewis argues, in ordinary discourse we speak of events as if robust	with respect to small enough changes in the manner	of	their	occurrence13	-	but	we	can	at	least	find	for	each	cause a different effect. A death is an instance of a highly determinable property,	and	one	might suggest that causing	a	death is	a	matter	of causing	one	of	its	determinates.	If	we	think	of	determinable	properties as supervenient properties, then this much follows from (DC). It's possible,	then,	for	two	marksmen	to	over-determine	a	death	by	each causing	one	of	its	determinates	at	the	same	time,	and	this	is	consistent with	holding	that	the	victim	would	have	died	the	same	death	had	one of	the	marksmen	missed.	Over-determining	causes	of	this	kind	have different	causal	roles.	Not	so	in	the	case	of	mental	causation,	it	seems: M	and	P	putatively	over-determine	P*	by	doing	exactly the same thing, viz. causing P*. Call this "redundant over-determination". The only remaining	option	is	to	deny	the	assumption	we	started	with,	viz.	that M	causes	P*.	But	by	(DC),	if	M	doesn't	cause	P*,	then	it	doesn't	cause M*	either,	and	there's	no	mental	causation. Kim	doesn't	have	a	knock-down	argument	against	redundant	overdetermination, but in earlier	work, he argues, based on a principle he	calls	"Alexander's	dictum",	that	if	mental	properties	have	no	novel causal	work	to	do,	we	should	eliminate	them:14 (AD) To	be	real	is	to	have	causal	powers. 12. Op. cit.	pp.	46–52. 13. Lewis	(1986). 14. Kim	(1992a,b). (DC) M causes	M* by causing its physical supervenience base	P*.8 Kim	needs two further	principles to	show	that	M	doesn't cause	M*. First,	the	causal	closure	of	the	physical: (CC) If	a	physical	event	has	a [complete, sufficient]	cause that	occurs	at	t,	it	has	a	[complete,	sufficient]	physical cause	that	occurs	at	t.9 On	the	assumption	that	M	causes	M*,	it	follows	from	(DC)	that	M	causes P*.	But	from	(CC),	P*	must	have	a	physical	cause	at	the	time	t	when	M occurs.	This	event,	P,	is	most	naturally	regarded	as	M's	supervenience base, but the simple version doesn't depend on this. One further principle	is	required,	the	oft-cited	"causal	exclusion	principle": (CX) No single event can have more than one sufficient cause occurring at any given time	-	unless this is a genuine	case	of	causal	over-determination.10 Assuming	that	M	and	P	both	cause	P*,	it	follows	from	(CX)	that	either M=P, or this is a genuine case of causal over-determination. Since functionalism is non-reductive, identifying	M and	P isn't an option. Identifying property instances entails identifying the properties they are instances of, since a property instance (x,P,Δt) is identical to	a	property instance (y,Q,Δt') if and	only if	x=y,	P=Q	and	Δt=Δt'.11 What about over-determination? Kim takes "genuine causal overdetermination" to involve	two	independent	causal	chains leading	to the	same	effect,	where	each	would	have	been	sufficient	in	the	absence 8. Kim	(2005)	p.	44. 9. Op. cit. p. 43. I	have	added the	parenthetical 'complete, sufficient' to	Kim's formulation	because	(a)	'sufficient'	is	clearly	implicit	in	that	formulation,	and (b)	without	'complete'	(CC)	would	be	consistent	with	certain	forms	of	emergentism,	according	to	which	mental	and	physical	causes	combine	to	cause	P*. I	return	to	the	completeness	of	physical	causes	in	(4). 10. Op. cit.	p.	41. 11. (x,P,Δt)	should	be	interpreted	as:	x's	having	P	during	interval	Δt. david	yates Functionalism and the Metaphysics of Causal Exclusion philosophers'	imprint – 4 – vol.	12,	no.	13	(july	2012) property of being a neuron doesn't, unless there's some incredibly complex structural property definable in terms of properties of fundamental	physics	that	all	neurons	have	in	common.	More	obviously, mental	properties	are	eliminated,	because	it's	hugely	implausible	that all those who like roast chestnuts share a physical property. Kim's causal exclusion argument, then, is a combination of two separate arguments: (i) an argument that mental property-instances are at best redundant over-determining causes; (ii) an argument that real, irreducible	properties	aren't	redundant,	so	that	mental	properties	are either	unreal	or	reducible.	Those	who	endorse	over-determination	as a response to the	exclusion	argument	accept (i)	but take issue	with (ii); those	who endorse difference-making causation can ignore (ii), because	they	reject	(i). 2.2. Humean solutions to the exclusion problem Humean solutions are Humean because they appeal to nomic or counterfactual relations between mental property-instances and behavioural	property-instances	to	show	that	mental	properties	do	causal work.	Such	strategies	typically	involve	(a)	defining	causation	in	terms of	laws	or	counterfactuals,	and	showing	that	according	to	the	definition, mental	property-instances	are	causes	of	certain	behavioural	effects;	and (b)	a tacit assumption that if	mental	property-instances	are causes	of behavioural	effects,	then	mental	properties	do	causal work	in	bringing those	effects	about.	I	grant	both	(a)	and	(b)	for	now,	but	in	Section	3, I	argue	that	(b)	is	demonstrably	false	on	an	independently	motivated account	of causal	work.	First, I'll	outline the	over-determination	and difference-making	solutions,	beginning	with	the	former. Those who think that M and P over-determine P* take this to mean that	M	does	causal	work, inheriting some	or	all	of the	causal power that P	has to cause	P*. Some	offer criteria of causal efficacy according	to	which	we	can	show	that	if	P	causes	P*,	then	-	given	the nature of the supervenience relation between	M and P	-	M causes P*.	Segal	and	Sober,	for	instance,	think	that	the	(possibly	non-strict) law	of	nature	that	M-instances	are	followed	by	M*-instances,	together According	to	(AD),	there	is	no	such	thing	as	an	entity	that	doesn't	cause (or	contribute	to	causing)	anything.	The	principle	may	seem	too	strong, since it rules	out the	existence	of	abstract	entities such	as	numbers, sets,	and	so	forth.	I	am	inclined	to	think	a	reasonably	circumscribed (AD)	can	avoid	such	problems:	we	might,	for	instance,	limit	its	scope to	natural	entities.	It's	one	thing	to	claim	that	some	entities	have	no causal powers, quite another to claim that mental properties have none.	I	needn't	worry	about	precisely	how	to	formulate	(AD),	however, since	my	aim	in	this	paper	is	to	show	that	mental	properties	have	novel causal	powers.	My	strategy	will	be	to	grant	the	(perhaps	implausibly) strong	version	of	(AD)	above	and	show	that	even	this	principle	does not	threaten	the	existence	of	mental	properties.	Kim	thinks	that	given (AD), their irreducibility implies that "mental properties bring	with them ... causal powers ... that no underlying physical-biological processes	can	deliver	...	.	[T]o	be	real,	new	and	irreducible	...	must	be to	have	new,	irreducible	causal	powers."15 If	cogent,	this	line	of	reasoning	rules	out	ontological	commitment to properties that are never	more than over-determining causes. If mental	properties	are irreducible	and	real, then their	causal	powers must	be	irreducible	as	well,	which	is	to	say	they	must	do	something their	realizers	don't.	According	to	functionalism,	mental	properties	are defined	by	roles	that	are	filled	by	physical	properties,	so	a	novel	causal role	seems	out	of	the	question. The upshot of the argument is that there are no functional properties.	The	only	properties	that	survive	the	cull	are	the	properties of fundamental physics, and any properties that are identical to particular	configurations	of	those	properties.16	The	property	of	being a	hydrogen	atom	survives,	as	does	the	property	of	being	H2O;	but	the 15. Kim	(1992a). 16. See	Kim	(2003),	where	he	argues	against	Block (2003) that causal	powers don't	"drain	away"	if	there's	no	fundamental	level.	This	is	because	Kim's	target	is	multiply	realizable	properties,	and	Kim	thinks	that	when	we	get	down sufficiently	deep,	there	won't	be	multiple	realization	any	more,	but	a	potentially	infinite	descent	through	mereological	levels	with	the	properties	of	each L	identical	to	structural	properties	of	L-1. david	yates Functionalism and the Metaphysics of Causal Exclusion philosophers'	imprint – 5 – vol.	12,	no.	13	(july	2012) base,	it	is	plausibly	metaphysically	necessary	that	if	anything	has	P,	it has	M.19 If there	are	no	P-occurs-without-M	worlds, conjunct (iii) is vacuously	true. The fact that M supervenes with metaphysical necessity on P also	-	on	the	assumption	that	M	inherits	P's	causal	efficacy	-	renders it unmysterious that there are two causes of P*. If widespread coincidence is the reason over-determination is problematic, not only	is	the	kind	of	over-determination	we	have	here	unproblematic; we also have a test	-	non-vacuous truth of all of (i)–(iv)	-	for the potentially problematic kind. Bennett takes a slightly different view, arguing that the	non-vacuous truth	of (i)–(iv) is necessary for overdetermination	simpliciter,	meaning	that	M	and	P	don't	over-determine P*	at	all.20	The	main	import	of	this	difference	relates	to	(CX).	Bennett must reject (CX)	-	M and P are distinct causes of, but don't overdetermine,	P*.	Kallestrup,	on	the	other	hand,	can	hold	that	M	and	P	do over-determine	P*,	but	in	a	way	we	shouldn't	worry	about.	It	matters little	for	my	purposes	precisely	what	'over-determination'	means. Assuming M inherits its causal powers from P, it remains only for over-determinationists to rebut Kim's redundancy argument. According	to	(AD),	nothing	lacks	causal	powers.	Functional	properties are	irreducible	to	their	bases.	Crucially,	Kim	takes	(AD)	to	imply: AD*: To	be	real	and	irreducible	is	to	have	irreducible	causal powers. But	as	others	have	pointed	out, (AD)	does	not imply	(AD*).21	From (AD),	it	follows	only	that	if	mental	properties	are	real	and	irreducible, then	they	have	causal	powers	and	are	irreducible.	As	Kallestrup	argues, there's	no	reason	to	take 'irreducible' to	qualify the	causal	powers	of 19. Kim	(2005)	attempts	to	block	the	argument	that follows	at this	stage,	arguing	that	M's	supervenience	on	P	is	nomologically	necessary	and	backed	by bridge-laws.	I	don't	find	this	persuasive,	but	haven't	the	space	to	take	up	the issue	here. 20.	Bennett	(2003). 21. Stephan	(1997);	Kallestrup	(2006). with	sufficiently	tight	supervenience	relations	between	M	and	P,	and between	M*	and	P*,	is	sufficient	for	M	to	cause	M*.17	This	theory	is supposed	to	account	for	the	causal	efficacy	of	mental	properties,	and so	is	intended	to	be	a	sufficient	condition	for	a	property	to	do	causal work.	M	inherits	causal	efficacy	with	respect	to	M*	from	P's	efficacy with	respect	to	P*,	via	the	supervenience	of	M	and	M*	on	P	and	P*, respectively,	together	with	a	law	relating	M	to	M*.	While	it	is	desirable to defend a theory of causation according to which M causes M*, most	over-determinationists	focus	on	showing	that	the	kind	of	overdetermination involved in	M causing	M* wouldn't be problematic. Kallestrup	thinks	of	over-determination	as	follows: (OD) E	is	over-determined	by	C1	and	C2	iff	(i)	C1	is	sufficient for	E,	(ii)	C2	is	sufficient	for	E,	(iii)	if	C1	had	occurred without	C2,	E	would	have	occurred,	and	(iv)	if	C2	had occurred	without	C1,	E	would	have	occurred.18 In firing-squad cases, all four conjuncts are non-vacuously true. There's	nothing	problematic	about	this,	because	we	know	why	these conjuncts	are	true	in	such	cases:	those	responsible	for	firing	squads act	precisely	so	as	to	make	them	true.	But	the	right-hand	side	of	(OD) is also non-vacuously satisfied in some cases without there being any explanation of why this is so. It's possible that two assassins independently decide to assassinate the same person at the same time without a common cause that might explain this. This too is unproblematic,	provided	it	doesn't	happen	very	often.	If	it	did,	there would be widespread inexplicable coincidence of forward-looking causal	powers,	which	-	grant	for	the	sake	of	argument	-	would	be	a very	bad	thing.	Now	M	and	P	satisfy	(OD)	with	respect	to	P*,	but	in a	different	way.	Let	P=C1,	M=C2,	P*=E.	Since	P	is	M's	supervenience 17. Segal	and	Sober	(1992).	Segal	and	Sober	think	in	terms	of	Davidson-events having	both	mental	and	physical	properties,	and	supply	a	sufficient	condition for	it	to	be	in	virtue	of	M	that	the	P∧M	event	causes	the	P*∧M*	event.	I	have recast	their	theory	in	terms	of	Kim-events	for	consistency.	See	also	Witmer (2003),	esp.	pp.	205	ff. 18. Kallestrup	(2006),	p.	471.	Adjusted	for	typographic	consistency. david	yates Functionalism and the Metaphysics of Causal Exclusion philosophers'	imprint – 6 – vol.	12,	no.	13	(july	2012) difference-making. Following List and Menzies, define differencemaking	as	follows,	where	F	and	G	are	property-instances:25 DM: F	makes	a	difference	to	G	iff:	(i)	F	occurs	*→	G	occurs, and	(ii)	¬(F	occurs)	*→ ¬(G	occurs) According to (DM), F	makes	a	difference to	G if and	only if the set of closest F	worlds to actuality are	G	worlds, and the set of closest non-F worlds are non-G worlds. Now let's evaluate the following counterfactuals: (i) M	occurs	*→	M*	occurs (ii) ¬	(M	occurs)	*→ ¬(M*	occurs) (iii) P	occurs	*→	M*	occurs (iv) ¬(P	occurs)	*→ ¬(M*	occurs) It's easy to see that (i), (ii), and (iii) are true.	The closest	M	worlds to actuality	will	be	worlds in	which	M is realized	by some	physical property	that	causes	a	realizer	of	M*;	the	closest	non-M	worlds	will be	worlds	where	it	has	no	physical	realizer	property,	and	at	which	no realizer	of	M*	occurs;	and	the	closest	P	worlds	will	be	worlds	at	which P* occurs.	However, the closest non-P	worlds to actuality	will	-	so the argument goes	-	be worlds at which some other realizer of	M occurs.	Intuitively,	this	seems	correct:	a	world	at	which	an	alternative realizer	P'	of	M	occurs,	which	is	similar	but	not	identical	to	P,	and	at which	an	alternative	realizer	P*'	of	M*	occurs,	is	closer	than	worlds	at which	neither	M	nor	M*	occurs.	But	if	this	is	so,	then	(iv)	is	false,	and P	doesn't	make	a	difference	to	M*. This	kind	of	argument	holds	wherever	causation	of	a	supervenient property-instance is involved, provided the occurrence of that property-instance	is	insensitive	to	the	precise	manner	of	its	realization. Interestingly,	such	cases	don't falsify (CX),	but that's	because	P fails to	be a cause	of	M*.	This is a case	of	M's	difference-making causal 25. List	and	Menzies	(2009);	Menzies	(2008). properties	rather	than	the	properties	themselves,	unless	of	course	we take the view that properties are exhausted by their causal powers. In that case, the	only thing that could	make	a supervenient	property irreducible	is	bestowing	causal	powers	its	base	property	doesn't.22	Overdeterminationists	can	reply	that	there	are	other	ways	for	a	supervenient property	to	secure	irreducibility	to	its	base.	Provided	M	can	inherit	the causal	powers	of	P,	and	M	has	a	kind	of	novelty	that	doesn't	require	it	to bestow	novel	causal	powers,	then	there's	no	pressure	to	eliminate.	We might,	for	instance,	endorse	Shoemaker's	subset	theory	of	realization, according	to	which	M	supervenes	on	P	because	its	causal	powers	are a	proper	subset	of	the	powers	of	P.	This	would	seem	to	preclude	our identifying	M and P, but whether it's enough to secure the kind of novelty	over-determinationists	need	is	a	moot	point.23 Those who endorse difference-making causation as a response to	the	exclusion	problem	follow	Yablo in	thinking	that	causes	must be proportional to their effects.24 M* has many distinct possible supervenience	bases,	of	which	P*	is	one;	similarly,	mutatis mutandis, for	M	and	P.	The	idea, informally, is	that	P	isn't	proportional	to	M*, because	P is causally sufficient for a specific realization	of	M*, viz. P*. Since	M*	might have occurred differently, P causally explains why M* happened in a particular way, but not why it happened simpliciter. Similarly, there will be property-instances that fail to explain	M*	due	to	not	being	specific	enough:	the	property	of	having some	mental property, for instance. The cause of M*, by contrast, ought to	be	a	property-instance that's just right, in the sense that it causes	M*	however	it	or	M*	are	realized,	and	M	fits	the	bill.	Yablo's notion of proportionality is typically now described in terms of 22. Kallestrup	(2006)	pp.	468–470 23. Shoemaker	(2001).	Kim	(2010)	suggests	that	Shoemaker's	theory	is	in	fact	a form	of	type-identity	theory,	but	these	matters	are	beyond	the	scope	of	this paper.	I	will	note,	however,	that	if	P	has	as	a	constituent	a	physical	property	P' whose	powers	are	the	same	proper	subset	of	P's	powers	that	M	inherits,	then there's	nothing	to	prevent	identification	of	M	with	P'. 24. Yablo	(1992). david	yates Functionalism and the Metaphysics of Causal Exclusion philosophers'	imprint – 7 – vol.	12,	no.	13	(july	2012) house	-	pushing,	lugging,	chopping	-	then	how	can	there	be	any	left for	M	to	do,	given	P's	sufficiency	for	P*?	But	that,	say	Humeans,	is	the wrong	way	to	think	about	causal	work.	Builders	certainly	do	this	kind of	work	when they	build	houses,	but that	doesn't	mean that	events do	it	in	causing	other	events.	As	Sider	points	out,	it's	surely	wrong	to think	of	causal	work	as	"a	kind	of	fluid	divided	among	the	potential causes	of	an	effect",	such	that	"[i]f	one	potential	cause	acts	to	produce an	effect,	that	fluid	is	used	up,	and	no	other	potential	cause	can	act".28 If that's	how	Kim	thinks	of	causal	work, then	the	burden	of	proof is on	him	to	show	that	this	way	of	thinking	is	more	plausible	than	the difference-making	theory	-	no	easy	task. Let's	take	stock.	There	are	two	solutions	under	consideration.	The first	says	that	M	and	P	both	cause	M*,	and	goes	on	to	say	either	that this	isn't	a	genuine	form	of	over-determination,	so	that	(CX)	is	false,	or that	it	is,	but	of	a	non-problematic	kind.	Still,	M	shouldn't	be	eliminated, because	it	can	earn	its	ontological	keep	without	being	causally	novel. The	second	says	that	M	is	causally	novel,	because	on	an	independently motivated theory	of	causation,	M	and	not	P	causes	M*,	and it	does so	without	causing	P*,	so	(DC)	is	false.	Both	strategies	assume	that	if we	can	show	that	an	appropriate	Humean	relation	holds	between	M and	M*,	then	we	will	have	shown	that	M	does	causal	work.	And	that's where	they	go	wrong. 3. Causal work and the inadequacy of the Humean response Humeans assume that if an instance of mental property M causes an instance	of behavioural property	B, then	M is causally efficacious with respect to	B, in the sense that it does the kind	of causal	work relating	to	B's	occurrence	that	exclusionists	say	it	doesn't	do.	I'll	now argue that this seemingly innocuous assumption is inconsistent with an independently plausible and widely held view concerning the kind	of causal	work that properties	do.	Most	philosophers	who think properties do causal work think that this work consists in 28.	Sider	(2003),	p.	721. role with respect to	M* excluding a similar difference-making role for P. What's gone wrong with the exclusion argument, then? It's not	obvious	what	we	should	say.	If	we	substitute 'difference-making cause' for 'cause' in (CC), then if we treat M* as a physical event (qua behavioural) then (CC) comes out false, because M* doesn't have	a	physical	difference-maker. If	we	substitute	difference-making causation	in	(DC),	it	too	comes	out	false.	M	isn't	a	difference	making cause	of	P*,	since	¬(M	occurs	*→	P*	occurs).	Perhaps	we	could	then keep	hold	of	(CC)	by	employing	a	more	flexible	notion	of	causation. There	is,	after	all,	a	sense	in	which	M*	does	have	a	sufficient	physical cause.	P	is	sufficient	for	P*,	and	the	supervenience	relation	between P*	and	M*	is	synchronic	and	non-causal,	so	it	would	seem	foolish	to deny	that	some	kind	of	causal	relation	holds	between	P	and	M*,	and	I see	no	reason	why	this	causal	relation	shouldn't	satisfy	proponents	of (CC).26	Let's	say	that	difference-making	causation	involves	a	rejection of	(DC):	M	causes	M*,	but	not	by	causing	P*,	so	there	isn't	any	overdetermination,	and	M's	causal	role	is	secure. But doesn't P still do all the causal work involved in M*'s occurrence? Well, not if causal work is understood as making a difference!	It's	a	fact	about	the	world	we	live	in	that	even	though	P* has	a	sufficient	physical	cause	P,	it	doesn't	follow	that	P	does	all	the causal	work involved in	M*'s occurrence, even though the relation between	P*	and	M*	is	non-causal.	Since	P	isn't	a	difference-making cause	of	M*,	M	has	novel	causal	power: it	makes	a	difference	to	M* that	nothing	else	does.	At	this	point	one	might	suspect,	with	Kim,	that difference-making causation is a cheat:27 the theory proposes two independent	levels	of	causal	work,	M	making	a	difference	to	M*	and P	making	a	difference	to	P*.	What's	odd	about	this	is	that	P	causally necessitates	M*,	in	the	sense	that	it	causes	something,	P*,	that	noncausally	necessitates	M*.	If	we	think	of	the	causal	work	required	for	M* to	happen	in	terms	of	the	kind	of	work	a	builder	has	to	do	to	build	a 26.	Yablo	calls	this	relation	"causal	sufficiency",	and	distinguishes	this	from	causation,	with	the	latter	requiring	proportionality	of	cause	and	effect. 27. Kim	(1998),	ch.	3. david	yates Functionalism and the Metaphysics of Causal Exclusion philosophers'	imprint – 8 – vol.	12,	no.	13	(july	2012) 3.1. Dispositions Famously,	sentences	of	the	form	'x	is	disposed	to	M	when	C',	can't	be analysed	in	terms	of	subjunctives	of	the	form	'were	C	to	occur,	x	would M'.31	Suppose	a	vase	is	disposed	to	shatter	when	struck	by	an	object	with momentum	≥ m,	and	label	this	disposition	DS.	(Hereafter	I	sometimes omit	'by	an	object	with	momentum	≥ m'	for	brevity.)	Suppose	the	vase has	DS	iff,	were	the	vase	to	be	struck,	it	would	shatter.	Finks	falsify	the putative	analysis	in	both	directions.	This	vase	is	Gandalf's	favourite,	and he'll	intervene,	whenever	it's	struck	by	an	object	whose	impact	would otherwise	have	shattered	it,	casting	a	spell	to	alter	its	atomic	structure	so that	it	doesn't	shatter.	Assuming	dispositions	are	intrinsic	properties,	the vase	has	DS	prior	to	being	struck,	but	the	analysans	isn't	satisfied.	Lewis proposes	that	the	simple	conditional	analysis	can	be	fixed	by	modifying the	analysans	to	'the	vase	has	an	intrinsic	property	P	such	that	were	it to	be	struck	and	retain	P,	it	would	shatter	because	of	its	having	P	and being struck'.32	Gandalf's favourite vase satisfies this analysans, so is disposed	to	shatter	when	struck,	even	though	it	doesn't.	However,	masks and	antidotes	falsify	the	revised	analysis	in	the	left-to-right	direction.33 Fragile	vases	can	be	wrapped	in	protective	packaging	so	that	they	don't shatter	when	struck.	Such	vases	retain	all	their	intrinsic	properties,	and ought	therefore	to	retain	their	dispositions,	but	Lewis'	analysis	entails that	such	vases	don't	have	DS.	Poisonous	substances	are	disposed	to	kill when	ingested,	but	don't	cause	death	when	taken	with	their	antidotes. But	antidotes	don't	alter	the	intrinsic	properties	of	poisons,	which	ought therefore	to	retain	their	disposition	to	kill	when	ingested. It's difficult to see how to rule out finks and antidotes in a principled	way.	A	mask	or	antidote	for	one	disposition	needn't	work on another. For this reason,	modifications that appeal to	normal or ideal	conditions,	or	(if	different)	ceteris paribus	clauses, tend	towards vacuity:	'the	vase	has	DS	iff	were	it	struck	in	ideal	conditions,	then	it 31. Martin	(1994). 32. Lewis	(1997);	simplified	for	exposition. 33. Johnston	(1992);	Bird	(1998). grounding	the	dispositions	of	their	bearers.29	This	is	a	commonplace, although	sometimes	stated	as	the	claim	that	properties	bestow	causal powers.30	The	central	idea	is	that	things	have	dispositions	to	issue	in certain	types	of	effects	when	appropriately	stimulated,	and	that	these dispositions	are	grounded	in	their	intrinsic	properties.	By	grounding the	dispositions	of	particulars,	efficacious	properties	thereby	ground causal	relations	involving	those	particulars. The	reader	may	worry	that	this	understanding	of	causal	work	isn't one	that	Humeans	would	accept,	so	a	little	clarification	of	my	aims	is	in order	before	proceeding.	I	think	there	are	good	independent	grounds for understanding causal work in terms of grounding dispositions, and that this	makes	good	sense	of	what	exclusionists	have in	mind when	they	say	there	isn't	any	causal	work	left	for	physically	realized functional	properties	to	do.	Thinking	of	causal	work	this	way	makes for persuasive arguments that neither the over-determination nor difference-making strategies work as responses to the exclusion problem. However, I don't appeal to causal work as grounding to argue against broadly	Humean approaches to	mental causation.	On the contrary,	what I propose to do is: (i) grant the exclusionists an independently	plausible	notion	of	causal	work	that	shows	why	neither the over-determination nor difference-making strategy solves the exclusion	problem;	(ii)	grant	Humeans	the	difference-making	theory	of event	causation;	and	(iii)	show	that	given	difference-making	causation, there's	plenty	of	novel	causal	work	for	functional	properties	to	do,	so that	Humeans	needn't	reject	the	view	that	properties	do	causal	work by	grounding	causal	powers. 29.	The	claim	that	dispositions	are	grounded	doesn't	entail	that	they	have	categorical	grounds.	My	position	is	consistent	with	dispositional	essentialism	about fundamental	properties,	which	I	can	understand	as	the	claim	that	such	properties essentially ground certain dispositions. See Shoemaker (1980); Bird (2007).	I	can	also	treat	fundamental	properties	as	pure,	ungrounded	powers, as	in	Molnar	(2003),	provided	such	powers	aren't	identified	with	dispositions in	my	sense,	and	so	can	be	thought	of	as	grounding	them. 30.	Shoemaker	(1980);	Wilson	(2002);	McLaughlin	(2006). david	yates Functionalism and the Metaphysics of Causal Exclusion philosophers'	imprint – 9 – vol.	12,	no.	13	(july	2012) has	DS.	Similarly,	a carefully	packaged	vase	needn't	be	so	packaged, so	according	to	(DISP)	will	have	DS	even	though	the	closest	worlds where	it's	struck	are	ones	where	it	doesn't	break. A prima facie	difficulty	arises	with	"reverse	finks".	Consider	a	cubic block	of	granite,	and	suppose	Gandalf	hates	the	block's	shape	so	much that	whenever	it's	struck,	he	changes	its	atomic	structure	so	that	the impact	is	sufficient	to	break	it.	The	block	has	an	intrinsic	property	-	its shape	-	in virtue of	which there's a range	of conditions in	which it would	shatter	when	struck,	so	the	stone	has	DS	after	all.	It	also,	however, has	intrinsic	properties	in	virtue	of	which	there's	a	range	of	conditions in which it wouldn't shatter when struck	-	a proper subset of the possible	conditions	in	which	no	wizard	hates	cubes.	What	this	means is	that	the	block	is	both	disposed	to	break	when	struck	by	an	object of	momentum	≥ m,	and	disposed	to	remain	intact	when	so	struck.	The disposition	to	M	when	C	is	not,	according	to	(DISP),	a	contradictory of the	disposition to	not-M	when	C	-	provided there's	no overlap in the	possible	background	conditions	in	which	it	would	M	when	C	and those	in	which	it	wouldn't.	Note	that	this	isn't	the	context-sensitivity others	have	pointed	out	in	the	satisfaction	of	predicates	like	'fragile'.37 A chair regarded by its Lilliputian designers as robust	will be seen as fragile	by	Gulliver,	but	both	can	agree that it's	disposed to	break when	Gulliver	sits	on	it.	They	will	simply	disagree	about	whether	this disposition	ought	to	be	counted	as	a	case	of	fragility.	That	things	can be	disposed	to	shatter	when	struck	and	disposed	to	not-shatter	when struck	has	nothing	to	do	with	this	kind	of	context-sensitivity,	but	does point	to	another	kind.	If	the	background	conditions	in	which	granite blocks	would shatter	when	struck	were likely to	obtain, rather than distant	nomic	possibilities,	we	might	well	regard	such	things	as	fragile. 3.2. Causal work as grounding dispositions I take grounding to be a transitive, irreflexive, and asymmetric relation which holds between facts	-	construed as things having 37.	Mumford	(1998);	Hawthorne	and	Manley	(2005). would	break'	isn't	terribly	informative	if	ideal	conditions	can	only	be specified	in	terms	of	their	enabling	the	manifestation	of	DS. 34	A	planet would shatter when struck in those conditions in which it would shatter	when	struck	-	even	if	no	such	conditions	are	possible.	All	of which	is	bothersome	for	me,	since	the	central	argument	of	this	paper depends	on	construing	causal	work	as	the	grounding	of	dispositions. Without	saying	something	about	dispositions, it	won't	be	clear	how properties	ground	them,	or	why	we	should	call it	causal	work	when they	do.	So	here	goes:35 (DISP) x is	disposed to	M	when	C iff	x has an intrinsic property P in virtue of which [there is a set of nomically possible background conditions {B1, ...	,Bk} such that if	x	were in	any	of the	Bi and	C occurred,	x	would	M.] (DISP) says nothing about the nature of the conditions in which x would M if C, except that they are nomically possible. Treat x's being in	such	conditions	as	a relational	property	of	x. I say that the intrinsic properties of things determine the range of conditions in which they	would	exhibit	certain	responses to	certain	stimuli.	More formally,	on	my	account,	the	grounding	property	P	of	the	disposition to M when C is an intrinsic physical property in virtue of which: $B1,	... ,Bk∀i[{Bi(x)∧C(x)}□→M(x)], where 1 ≤ i ≤ k. (DISP) handles finks	and	masks.	Assume for the	sake	of	argument that	wizards	are nomically possible.36 No vase is necessarily Gandalf's favourite, so even	a	vase	protected	by	Gandalf	has	intrinsic	properties	in	virtue	of which	there's	a	range	of	nomically	possible	conditions	such	that	if	it were	struck	in	those	conditions,	it	would	shatter.	Such	a	vase	therefore 34.	Martin	(1994);	Fara	(2005). 35. My	central	arguments	will	go	through	on	other	accounts	of	dispositions,	for instance	Lewis	(1997);	Fara	(2005).	In	general,	my	account	will	work	for	any account	of	dispositions	that	explains	(i)	their	grounding,	(ii)	the	relationship between	grounding	dispositions	and	causality. 36. It	doesn't	matter	if	the	actual	laws	of	nature	rule	out	wizards,	because	I	want (DISP)	to	be	true	at	worlds	where	the	laws	of	nature	that	hold	there	don't. david	yates Functionalism and the Metaphysics of Causal Exclusion philosophers'	imprint – 10 – vol.	12,	no.	13	(july	2012) that	there	are	conditions	in	which	it	can	shatter	objects	incapable	of absorbing	more	than	a	certain	amount	of	energy	without	shattering. It's because these two sets of conditions overlap that hammers are best	kept	in	the	shed,	where	there	are	no	vases.	Let's	turn	now	to	the question	of	what's	causal	about	causal	work	as	I	understand	it. Ordinary	causal	talk	enables	us	to	identify	properties	that	ground dispositions, and the stimulus conditions of those dispositions, as causes.41 In 'the vase broke because of its atomic structure' we do the former; in 'the	hammer's impact caused the	vase to shatter', the latter.	Thinking	of	the	relata	of	causation	as	property-instances	blurs this	distinction:	the	locution	'the	vase's	having	the	property	of	being struck	by	a	hammer	with	momentum	≥ m'	refers	not	only	to	properties that	do	causal	work	in	grounding	the	power	of	the	hammer	to	shatter the	vase,	but	also	to	the	stimulus	condition	of	that	disposition	-	the striking	of	the	vase	by	the	hammer.	Whether	or	not	this	condition	is	met makes	a	difference	to	whether	or	not	the	vase	shatters.	Since	stimulus conditions	don't	ground	the	dispositions	whose	stimulus	conditions they	are,	but	do	make	a	difference	to	their	manifestations,	it	follows right	away	that	there	are	difference-making	causes	that	do	no	causal work, which should give us grounds for doubting the differencemaking	solution	to	the	exclusion	problem.	I	don't	depend	on	this	in what follows, however, and for now will focus on how grounding dispositions	also	grounds	difference-making	causal	relations	between stimulus	conditions	and	manifestations. A vase's intrinsic properties determine a range of possible conditions	such	that	were	it	struck	in	any	of	those	conditions,	it	would shatter.	Suppose	such	a	condition	obtains	at	the	actual	world,	and	that a	vase	is	struck	and	shatters.	The	closest	possible	worlds	to	actuality	at which	the	vase	is	struck	will	be	worlds	at	which	the	same	background conditions	hold:	the	vase	isn't	bubble-wrapped,	and	it	isn't	Gandalf's favourite.	Clearly the	vase	will	also	have	DS	at these	worlds,	and	so shatters. Hence, at our	world the vase is such that (a) had it been 41. We	can	also	identify	the	dispositions	themselves	as	causes.	More	on	this	in Section	3.4. properties	-	and	reflects	ontological	priority.38	If	an	entity	x	having	a disposition	D	is	grounded	in its	having	some	property	P, then	x	has D	in	virtue	of	having	P,	and	x's	having	P	is	more	fundamental	than	its having	D.	Since	grounding	entities	are	more	fundamental	than	those they	ground,	nothing	can	be	its	own	ground.	(Fundamental	entities	are ungrounded,	not	self-grounding.)	Further,	if	P	grounds	D,	it	can't	be	the case	that	D	grounds	P;	for	otherwise	each	would	be	more	fundamental than the other. So understood, grounding	must be both irreflexive and	asymmetric.	I	hold	that	grounding	is	transitive	because	I	take	X's ground	to	be	a	metaphysically	explanatory	reason	for	X.	If	psychology is	grounded	in	neuroscience,	for	instance,	then	neuroscience	explains why we have psychological properties. But if psychology, in this sense,	grounds	economics,	then	I	take	that	to	imply	-	at	least	in	some sense	-	that	neuroscience	explains	economics.39 Intrinsic properties determine how things would respond to various	stimuli	in	a	range	of	nomically	possible	circumstances.	Loosely speaking, the vase's atomic structure grounds	DS by	being the kind of	structure	that	can't	absorb	more	than	a	certain	amount	of	energy without undergoing the kind of rearrangement that counts as a shattering.	Having	this	structure	determines	that	there	are	conditions in	which	the	vase	would	break	when	struck	by	objects	that	have	at	least that	much	energy	to	give.	These	conditions	will	include	that	nothing (such	as	bubble	wrap)	prevents	the	vase	from	absorbing	the	energy	of the	striking	object;	that	no	wizard	loves	the	vase	so	much	he'll	change its structure so that it can absorb the energy without shattering; and	so	on.	Since	dispositions	manifest reciprocally,40 the same	goes mutatis mutandis for the striking object	-	a hammer, say	-	whose properties	will	determine	how	much	energy	it	can	transfer,	in	a	range of conditions, to objects it strikes. Its properties thereby determine 38. I'll	often	speak	of	properties	grounding	other	properties,	but	this	is	shorthand. 39. I	say	more	about	the	difference	in	the	sense	of	'grounds'	between	(e. g.)	'neuroscience	grounds	psychology'	and	'neuroscience	grounds	economics'	in	Section	4.2,	where	I	distinguish	proximal	from	distal	grounding. 40.	Heil	(2005);	Martin	(2007). david	yates Functionalism and the Metaphysics of Causal Exclusion philosophers'	imprint – 11 – vol.	12,	no.	13	(july	2012) ionizing them by ejecting electrons, resulting in a positive charge. My	point	here is that it isn't the energy of the	photon that transfers energy to	electrons in the tissues, causing their	ejection.	Having	an energy greater than 1.022MeV	merely disposes the photon to bring about	pair	production	when	appropriate	conditions	obtain,	which	in turn	produces	electrons that are	disposed to	bring	about ionization of	tissues	when	further	such	conditions	obtain.	Properties	ground	the dispositions of particulars, thereby determining the range of causal interactions	in	which	they	could	be	involved. 3.3. Functional realization as causal work Functional properties are physically realized, and their realizers do all the causal work associated with their defining roles. Given that causal	work is grounding dispositions, it follows that realizers ground	all	the	dispositions	particulars	need	in	order	to	enter	into	roledefining	causal	relations.	We	might	say	that	physical	properties	realize functional properties by grounding a certain characteristic set of dispositions,	with	realization	ontologically	dependent	on	grounding. In	this	section,	I	argue	that	this	is	double-counting,	because	realization and grounding are the same relation. I first argue that functional properties,	as	typically	construed,	are	sets	of	dispositions,	and	proceed to	show	that	given	this,	realizing	a functional	property is	grounding it.	Functional	properties	don't	just	depend	upon	the	causal	work	their realizers	do, they are (at least some	of) that work.44	As	we'll see, this identity	of	realization	and	causal	work	renders	the	over-determination and difference-making strategies ineffectual against the exclusion argument. It also paves the way for my positive theory of mental causation,	which I present in part (4). The arguments I give below depend	on	(DISP),	although	they	could,	I	think,	be	adapted	to	other broadly	Humean	theories	of	dispositions.	(DISP)	suggests	(although it	doesn't	entail)	that	dispositions	are	second-order	properties;	I	treat them	as	such	in	what	follows. 44.	Many	are	prepared	to	accept	without	argument	that	functional	properties	are complex	dispositions.	See	for	instance	McLaughlin	(2006). struck, it would have shattered. The vase's intrinsic properties also determine	other	dispositions,	such	as	the	disposition	to	remain intact, DI,	when	struck	by	an	object	of	momentum	<	m,	or	no	object	at	all. There	will	be	significant	overlap	in	the	background	conditions	for	DS and	DI; in fact,	DI	was	manifesting right	before the	vase	was struck. Given	that	the	shattered	vase	was	in	background	conditions	for	both DI	and	DS,	it	follows	straight	away	(assuming	also	that	it's	in	the	same conditions	at	the	closest	worlds	to	actuality	where	it	isn't	struck)	that (b)	had	it	not	been	struck,	it	wouldn't	have	shattered.	Now	given	the difference-making theory of causation, it's clear how grounding an object's dispositions also grounds its causal potentialities, because (a)	and	(b)	are	jointly	necessary	and	sufficient	for	the	striking	to	be	a difference-making	cause	of	the	shattering.42 One might object at this point that it is things, not properties, that	do	causal	work.	The	hammer	exerts	a	force	on	the	vase,	thereby transferring	energy	to	it	-	an	informal	version	of	the	physicist's	notion of	work.	The	exclusion	problem,	however,	depends	on	there	being	a sense	of	'causal	work'	that	makes	it	true	that	properties	do	causal	work, and transferring energy isn't it. To see this, consider that energy is itself	a	causally	efficacious	property	par	excellence.	Gamma-rays	cause skin	burns	and	radiation	sickness	in	virtue	of	their	high	energy,	and the	causal	processes	by	which they	do	so involves transfer	of some of that very energy to the unfortunate victim.	One such process is pair	production,	whereby	a	photon	of	energy	greater than 1.022MeV interacting	with	a	heavy	nucleus	produces	an	electron-positron	pair.43 The electron, for instance, may then interact with organic tissues, 42. There	will	be	other	Humean	theories	of	causation	and	dispositions	that	have the	same	explanatory	virtues,	so	my	central	arguments	don't	depend	on	the present	ones	being	correct.	Perhaps the reader is	prepared to	accept,	without	a	particular	theory	of	causation	or	of	dispositions,	that	what	grounds	x's disposition	to	M	when	C	thereby	grounds	the	causal	relation	that	obtains	on some	occasion	when	C	occurs	and	x	Ms. 43. Gamma	photons	of	energy	greater	than	2mec 2	are	required	(where	m is the electronic	mass,	and	c	the	speed	of	light),	with	the	energy	of	the	photon	being converted,	according	to	Einstein's	energy-mass	equation,	into	the	rest	masses of	the	electron	and	positron.	The	details	needn't	concern	us	here. david	yates Functionalism and the Metaphysics of Causal Exclusion philosophers'	imprint – 12 – vol.	12,	no.	13	(july	2012) we	only	need	to	Ramsify	away	the	mental	predicates,	and	the	causalnomic	ones	aren't	mental.45	So	far,	I	claim	only	that	if	(2)	is	to	define a	functional	property,	R(T)	must	specify	the	causal	structure	that	the properties	P1,	... ,Pn	must satisfy in	order to count as realizers	of F1, ... ,Fn. But now if, as I am	assuming, causation is difference-making, then	R(T)	must	contain	a	conjunction	of	subjunctives	specifying	the differences physical properties need to make in order to count as realizers	of	mental	properties.	Suppose	for	the	sake	of	argument	that T	is	folk-psychology,	and	that	part	of	what	T	claims	about	the	property W	of	wanting	some	X is	that	given	a	specified	psychological	state	FT, wanting	X	causes	so	acting	as	to	acquire	it.46	Given	difference-making causation,	this	component	of	T	can	be	written: (S) ∀x[{[FT(x)	∧	W(x)]	□→	A(x)}	∧	{[FT(x)	∧ ¬W(x)]	□→	¬A(x)}] where	A	is	the	property	of	so	acting	as	to	acquire	X.	Holding	FT	fixed, wanting	X	makes	a	difference	to	whether	you	try to	get it.	R(T)	will preserve this subjunctive structure as a constraint on the Pi , so (2) defines functional properties by	means of subjunctive conditionals, which is how (1) defines dispositions. My argument assumes that Ramsey sentences specify causal structure using causal predicates. Readers persuaded that psychological theories have an explicitly subjunctive	form	won't	need	to	commit	to	this	claim,	or	the	differencemaking	theory	of	causation,	to	see	this	similarity	between	(1)	and	(2). 45. The	reader	will	be	reminded	here	of	the	familiar	Newman	objection	to	structural realism in the	philosophy	of science. Structural realists often employ Ramsey	sentences	to	define	theoretical	terms,	but	if	the	non-theoretical	terms left	un-Ramsified	consist	solely	of	logical	and	observational	(in	the	positivists' sense) vocabulary, then it's provable that the Ramsey sentence constrains only	the	cardinality	of	the	theoretical	domain.	These	matters	are	beyond	the scope	of	this	paper,	but	note	that	structural	realists	wanting	to	avoid	the	Newman	objection	can	argue	that	causal	vocabulary	belongs	in	the	O-language and	so	shouldn't	be	Ramsified. I	needn't	argue	anything	so	strong: for	my purposes	it	suffices	that	the	causal	vocabulary	isn't	in	the	F-language,	i. e.,	that it's	non-mental.	See	Papineau	(2010),	pp.	381–2	for	discussion. 46. FT	will	be	a	conjunction	of	other	mental	properties	such	as	not	having	stronger	desires for	not-X,	believing that the	actions	necessary to	acquire	X are morally	permissible,	etc. Using	'λx.p'	to	denote	the	property	of	being	an	x	such	that	p,	letting the existential quantifier range over intrinsic physical properties, and	where	1	≤ i ≤ k,	we	can	represent	the	disposition	D	to	M	when C	as	follows: (1) D	=	λx.$P[P(x)	∧	{$B1,	...	,Bk∀i[{Bi(x)	∧	C(x)}	□→	M(x)]	in virtue	of	P}] Given	(1),	D	is	the	property	of	having	an	intrinsic	property	P	in	virtue of	which	there	exist	conditions	such	that if the	bearer	were	in	them and	subject	to	C,	it	would	M.	Functionalism	about	the	mind	is	typically characterised	by	appealing	to	psychological	theories:	a	given	functional property	is	the	property	of	having	some	property	that	occupies	a	causal role specified (in a way to be clarified) by that theory. In the now standard	way,	let's	write	the	theory	(whatever	it	may	be)	as	T(F1,	...	,Fn; O1,	...	,Om),	where	the	F-terms	are	the	predicates	that	denote	mental properties,	and	the	O-terms	are	everything	else.	Replacing	the	F-terms with appropriately indexed variables, and prefixing the resulting formula	with an existential quantifier, we get T's Ramsey sentence, R(T):	$P1,	...	,Pn[T(P1,	...	,Pn;	O1,	...	,Om)].	Functionalists	define	the	ith mental	property	Fi	as	follows: (2) Fi	=	λx.[$P1,	...	,Pn[T(P1,	...	,Pn;	O1,	...	,Om)	∧	Pi(x)] Given (2), Fi is the property of having some other property that occupies	a	specific	place	in	a	network	of	states	that	jointly	satisfy	T.	It isn't	immediately	obvious	from	(1)	and	(2)	that	functional	properties are dispositions, but I'll now argue that on reasonable assumption, they	are.	I	don't	have	anything	like	a	proof;	rather,	I	suggest	a	series of further constraints on (2) if it is to adequately define functional properties,	with	each	one	bringing	it	closer	to	(1). In	order	to	define	a	specific	functional	property	Fi ,	the	right-hand	side of	(2)	must	specify	a	causal-nomic	structure	and	the	part	of	it	occupied by	Fi 's	realizer	Pi .	For	this	to	be	the	case,	the	O-language	must	contain causal-nomic predicates. This isn't a problematic requirement here, because	for	present	purposes	the	definienda	are	mental	properties,	so david	yates Functionalism and the Metaphysics of Causal Exclusion philosophers'	imprint – 13 – vol.	12,	no.	13	(july	2012) are properties of the same agent	-	then T encodes such stimulus conditions in virtue of quantifying over agents. Perhaps	we can do better.	Suppose	I	want	some	food,	but	don't	yet	know	it	-	distracted by	philosophical	theorising,	I	haven't	reflected	on	my	current	desires. Part	of the	psychological	state	FT relative	to	which	my	wanting	food makes	a	difference	to	my	having	some	will	be	my	entertaining	both the	desire	and	the	rest	of	FT.	Perhaps	jointly	entertaining	beliefs	in	a deliberative process is, in a sense, bringing them into contact	with each	other.	If	so,	then	T	will	contain	terms	for	conditions	analogous	to the	stimuli	such	as	contacts,	impacts,	and	so	forth,	to	which	we	appeal when	defining	dispositions	like	fragility. And	finally,	(c).	I	treat	the	realizers	of	the	disposition	to	M	when	C as	determining	a	range	of	conditions	such	that	if	their	bearers	were	in those	conditions	and	C	happened,	they	would	M.	As	we	saw	in	Section 3.1,	this	enables	my	approach	to	deal	with	finks	and	masks.	I	argued above that if	R(T) is to	define	a	causal	structure, then	T	must	make general	causal	claims	about	mental	properties,	and	hence,	assuming difference-making causation, must imply subjunctive claims of the form	given in (S). I	omitted	ceteris paribus (cp)	clauses for simplicity, but	it's	now	time	to	put	them	back	in.	Since	the	psychological	domain isn't causally closed,	T	must contain implicit cp clauses	-	there isn't a	conjunction	of	psychological	properties	such	that	if	you	have	all	of them,	then	wanting	food	makes	the	appropriate	difference	to	eating. Suppose,	for	instance,	that	there's	a	drug	-	backwards powder	-	whose primary	effect	is	that	humans	who	have	FT	and	ingest	it	are	such	that if	they	wanted	food,	they	wouldn't	have	any,	and	if	they	didn't,	they would.	We might deal with the implicit cp clauses in T by simply incorporating them into (2), qualifying the truth of the relevant subjunctives.	Or,	as	I	prefer,	we	could	deal	with	them	by	saying	that the realizer	properties	P1,	... ,Pn aren't	properties in	virtue	of	which those	subjunctives	hold,	but	properties	in	virtue	of	which	there	exist a	range	of	conditions in	which	they	hold.	One	such	condition, for	us, is	the	absence	of	backwards	powder,	but	this	isn't	so	for	all	possible realizers	of	our	mental	states.	Martians	are	a	case	in	point:	on	Mars, Several	differences	remain:	(a)	(2)	doesn't	say	anything	about	its	being in virtue of	the	Pi	that	the	specified	causal	structure	obtains,	and	makes no explicit mention of (b) stimulus conditions, or (c) background conditions.	I'll	now	briefly	address	these	points	in	turn. First, (a). It's widely supposed in the literature that Ramsified theories	can	fully	define	physically	realized	functional	properties,	but if	causation	is	difference-making	(or	more	generally,	Humean), then this isn't so. The reason is that implicit in the notion of realization is the claim that the physical realizers of a functional property do all	the	causal	work	associated	with	the	role	that	defines	it.	That,	as	I said,	is	why	there's	a	causal	exclusion	problem.	In	the	next	section	I'll present	an	argument	that	doesn't	depend	on	the	view	that	functional properties	are	dispositions	(and	one	that	does)	to	the	effect	that	making a	difference	(or	more	generally,	standing	in	a	Humean	causal	relation) to	some	effect	isn't	sufficient	for	doing	any	of	the	causal	work	involved in its	occurrence.	This	being	so, if the	Ramsey	sentence	only	places Humean	causal	constraints	on	the	realizers,	its	truth	will	be	consistent with	those	realizers	not	doing	any	of	the	causal	work	associated	with the	roles	they	realize.	In	addition	to	such	causal	claims,	then,	we	need to	include	in	(2)	the	further	stipulation	that	the	Pi	stand	in	their	various role-defining	causal	relations	in virtue of	the	Pi . Let's	move	on	to	(b).	(1)	characterises	a	disposition	D	in	terms	of	a stimulus	condition	C	and	manifestation	M,	whereas	(2)	characterises a functional property Fi in terms of a network of physical states, causally related (in virtue of their physical properties) as specified in T. I claim that the Fi , so understood, are dispositions, which will sometimes manifest as behaviour, sometimes as other Fi ; but where are their stimulus conditions? What makes for the prima facie disanalogy between (1) and (2) is that it's natural to think of hammers	as	having	dispositions	to	break	vases,	which	have	reciprocal dispositions to be broken	by	hammers; and in addition to suppose that	the	stimulus	conditions	of	these	dispositions	are	that	their	bearers come	into	contact.	Where's	the	psychological	analogue?	Suppose	the stimulus	condition	of	psychological	dispositions	are	simply	that	they david	yates Functionalism and the Metaphysics of Causal Exclusion philosophers'	imprint – 14 – vol.	12,	no.	13	(july	2012) for the dispositions itself to do. All the causal work is being	done	by	the	bonding	P	together	with	the	dropping. Why, goes the standard over-determinationist response, can't the fragility (F)	do the same causal	work	as	P? Jackson	doesn't say,	but given	that	the	causal	work	of	P	consists	in	grounding	F,	the	answer	is clear:	because grounding is irreflexive. It isn't just	that	there's	no	causal work	left	for	F	to	do;	there	doesn't	seem	to	be	any	work	it	could	possibly do.	We	can	now	see	why	Humean	theories	of	causation	don't	capture the	notion	of	causal	work	at	stake	in	the	exclusion	argument.	Suppose, for	instance,	that	the	nomic-subsumption	theory	of	causation	is	true. Dispositions	supervene	on their	physical realizers	and	are	plausibly lawfully	related	to	their	own	manifestations,	but	they	are	patently	not self-grounding.	The	same	goes	mutatis mutandis	for	any	counterfactual theories, such as the difference-making theory, which entail that dispositions	cause	their	own	manifestations.48 Difference-making	theories	of	causation,	when	taken	as	sufficient conditions on causal work, imply that dispositions do causal work their	realizers	don't.	Consider	the	fragility	of	the	vase	F	and	its	physical realizer P. Assuming the vase's shattering, S, is realizer-invariant, F makes	a	difference	to	S	that	P	doesn't.	The	closest	non-F	worlds	are non-S worlds, and the closest F-worlds are S-worlds, which is all that's	required	for	F	to	make	a	difference	to	S.	By	contrast,	the	closest non-P worlds are worlds where some other realizer P' of F occurs, together	with	a	different	realizer	of	S.	Since	the	closest	non-P	worlds are	S-worlds,	P	doesn't	make	a	difference	to	S.	F	indexes	the	vase	to a	different	portion	of	modal	reality	than	P,	and	so	makes	a	difference to	S that	P	doesn't.49	That	dispositions	are	difference-making	causes of	their	manifestations	shows	that	making	a	difference	isn't	sufficient 48. The	reader	may	worry	that	dispositions	aren't	causally	relevant	to	their	manifestations,	but	as	McKitrick	(2005)	argues,	independently	plausible	theories of	causal	relevance	imply	that	they	are.	If	we	treat	difference-making	as	an account	of	causal	relevance,	it's	a	case	in	point. 49. This	will	prove	important	in	Section	4.4. backwards	powder is a	naturally	occurring	mineral the ingestion	or non-ingestion	of	which	makes	no	difference	at	all	to	whether	or	not they	satisfy	T. Functionalist mental properties are, I conclude, a complex kind of	dispositional	property.	Not,	it	must	be	said,	the	property	of	having a	property in	virtue	of	which	there	are	conditions in	which	a certain subjunctive is true; rather, the property of being in one of a range of states in virtue of which, collectively, there exist conditions in which	a	large	conjunction	of	subjunctives	is	true.	But	they	are	no	less dispositional	for	their	added	complexity. 3.4. Why Humean causation isn't sufficient for causal work Although I endorse the difference-making theory of causation, finding	causal	work	for	a	property	to	do	is	harder	than	showing	that its instances	are causes. I argued	above that (A) the	causal	work	of properties consists in grounding dispositions; and (B) functional properties are complex, physically realized dispositions. It follows from	(A)	and	(B)	that	functional	realization	is	grounding:	functional properties	are	(at	least	some	of)	the	causal	work	that	their	realizers	do. This	licenses	a	simple	argument	for	the	view	that	(C)	being	a	Humean cause	of	some	effect	isn't	sufficient	for	doing	any	of	the	causal	work involved	in	its	occurrence.	Those	who	argue	against	the	causal	efficacy of dispositions, construed as second-order functional properties, simply	employ	the	exclusion	argument.	Here's	Jackson: 47 Consider	...	a	fragile	glass	that	shatters	on	being	dropped because it is fragile	... .There	will be	... a certain kind of bonding P between the glass's molecules which is responsible	for	the	glass	being	such	that	[it	breaks	when dropped]	...	.	But	then	it	is	bonding	P	together	with	the dropping that	causes the	breaking; there is	nothing left 47. Jackson	(1996),	p.	393.	Adjusted	for	typographic	consistency.	See	also	Prior, Pargetter	and	Jackson	(1982);	McLaughlin	(2006). david	yates Functionalism and the Metaphysics of Causal Exclusion philosophers'	imprint – 15 – vol.	12,	no.	13	(july	2012) in grounding	Di , and again, since grounding is asymmetric and	Di grounds	F,	this	is	work	that	F	simply	can't	do.51 At	this	point	one	might	suggest that	expecting	mental	properties to	do causal	work in	my sense is expecting too	much.52 If this is to provide	for	a	reply	to	the	exclusion	argument,	then	if	we	understand	a property's	having	causal	powers	in	terms	of	its	doing	causal	work,	and understand	causal	work	in	terms	of	grounding	dispositions,	then	we'll have	to	reformulate	(AD),	because	as	things	stand	(AD)	requires	real, irreducible	properties	to	be	irreducible	and to have causal powers.	This amounts	to	accepting	different	standards	for	functional	properties	and at least	some	physical	properties.	Physicists, for instance,	commit to properties	on	the	basis	of	genuinely	novel	causal	work,	but	perhaps these standards aren't appropriate in psychology. This approach attempts to solve the exclusion problem by admitting that mental properties	do	no	causal	work,	then	arguing	that	this	doesn't	result	in their	elimination	because	the	conditions	for	ontological	commitment to	such	properties	are	looser	than	those	for	physical	properties.	Setting psychology aside, science isn't all physics, and there are plenty of functional properties in biology and neuroscience that don't earn their	ontological	keep	in	the	same	way	their	realizers	do,	but	to	whose existence	biologists	and	neuroscientists	are	nonetheless	committed. I	have	a	certain	sympathy	with this	way	of thinking,	but it	won't do	anything	to	convince	the	determined	exclusionist,	who	will	simply reply that when it gets down to brass tacks, there aren't really any biological	or	neuroscientific	properties	either.	Retreating	to	the	position that functional properties earn their keep by making a difference, despite	the	fact	that	they	do	no	causal	work,	reduces	the	disagreement between	exclusionists	and	Humeans,	which	used	to	be	about	whether there's	any	causal	work	left	for	functional	properties	to	do,	to	one	about what	our	standards	for	ontological	commitment	to	properties	ought	to 51. It	should	be	noted	that	my	arguments	against	both	the	over-determination and	difference-making	strategies	tell	only	against	the	use	of	these	strategies to	account	for	the	efficacy	of	functional	(i. e.,	dispositional)	properties. 52. LePore	and	Loewer	(1987). for doing causal work. The property F is the glass's disposition to shatter when dropped, and so, since grounding is irreflexive, can't ground that disposition. Difference-making causation identifies the causal	work	done	as	a	cause,	which	seems	right.	Causal	work	makes a	difference	to	what	happens;	if	it	didn't,	what	would	be	the	point	of doing	it?	But	this	means	we	shouldn't	expect	all	difference-makers	to do	the	kind	of	causal	work	the	exclusion	argument	denies	to	mental properties.50	Conversely,	not	all	properties	that	ground	a	disposition make	a	difference	to	its	manifestations. It	will	be	noted	that	in	Section	3.3,	I	presupposed	(C)	above	as	part	of my	argument	for	(B).	But	the	argument	for	(C)	just	given	presupposes (B),	so I	still	owe	the	reader	a further	argument for (C) that	doesn't depend	on	(B).	I'll	now	argue	that	(C)	follows	from	(A)	alone,	together with	the	reasonable	claim	that	realization	is	a	form	of	grounding,	even if functional properties aren't dispositions. Functional property F is the	property	of	having	some	property	P	with	causal	role	R.	For	P to have	causal	role	R,	given	(A),	is	for	it	to	ground	the	dispositions	that characterise	R:	label	this	set	of	dispositions	Di .	Given	that	P	realizes F	by	doing the	causal	work	associated	with role	R, it follows that	P realizes	F	by	grounding	Di .	It	doesn't	matter	which	P	grounds	Di	-	it's Di	that	really	matters	to	F's	realization.	Since	F	ontologically	depends on	Di ,	and	having	Di	(grounded	by	some	P)	is	sufficient	for	having	F, it	follows	that	Di	grounds	F.	The	reason	why	F	can't	inherit	the	causal work of P is simple: because grounding is asymmetric. F ontologically depends on the causal	work that P does, so the supposition that F inherits	this	work	from	P	is	incoherent.	Similar	considerations	apply mutatis mutandis	to	the	difference-making	strategy.	For	familiar	reasons, F	will	make	differences	to	the	manifestations	of	the	dispositions	in	Di that	P	doesn't.	But	from	this	we	can't	infer	that	F	does	any	of	the	causal work required for those manifestations, since that work consists 50.	Crane	makes	a	similar	point	concerning	counterfactuals	and	the	causal	efficacy	of	properties	in	his	(2008).	Crane's	arguments	for	this	conclusion	aren't related	to	mine. david	yates Functionalism and the Metaphysics of Causal Exclusion philosophers'	imprint – 16 – vol.	12,	no.	13	(july	2012) Now if we interpret Alexander's Dictum (AD) as the claim that properties	must do at least some causal	work (novel or otherwise) in order to earn their ontological keep, it seems to follow straight away that functional properties ought to be eliminated, since: (i) supervenient	properties	in	general	can't	do	causal	work	their	physical bases	don't	do,	since	that	would	render	them	ontologically	emergent, violating	causal closure; (ii) functional	properties can't	do the same causal	work as their realizers, since they	are (at least some	of) that work. True, functional properties make a difference their realizers don't, but that doesn't matter, because making a difference isn't sufficient	for	doing	causal	work,	and	it's	precisely	because	they	seem to do no causal work that functional properties face the threat of elimination. I now present a theory according to which functional properties	do	novel	causal	work	without	grounding	any	dispositions that	aren't	grounded	in	the	physical,	and	so	without	doing	any	causal work	that	physical	properties	don't	do.	According	to	this	theory,	the causal	novelty	of	functional	properties	consists	not	in	the	dispositions they	ground,	but	in	the	level,	within	a	hierarchy	of	grounding	relations, from	which	they	ground	them.	I	call	it	upwards causation. 4.1. Upwards Causation54 I	will	say	that	a	mechanism	X	is	individuated	by	(i)	possession	of	a	set D	of	dispositions,	and	(ii)	a	set	of	components	{x1,	...	,xn},	each	having further	sets	of	dispositions	{D1,	...	,Dn},	such	that	{x1,	...	,xn}	having	{D1, ...	,Dn}	constitutively	explains	why	X	has	D.	Suppose	I	wish	to	construct a mousetrap using the following items: (a) a 1,000,000V battery, (b) conducting	wire	of resistance 10Ω, (c) a thin sheet	of copper	of negligible	resistance.	I	first	cut	the	wire	in	two,	and	attach	one	end	of one	piece	to	the	positive	terminal	of	the	battery,	one	end	of	the	other to	the	negative.	I	then	attach	the	other	end	of	the	positive	wire	to	the sufficiency)	and	synchronic	causal	work	(completeness).	See	Yates	(2009)	for detailed	discussion. 54. The	account	I	give	here	owes	much	to	Craver's	(2007),	in	particular	chapters 4	and	5,	but	I	don't	attribute	what	follows	to	him. be.	Far	better for	Humeans to	grant	exclusionists the	more	stringent condition and then show that functional properties meet it. In the remainder	of	this	paper,	I	argue	that	higher-order	functional	properties can	do	the	same	kind	of	causal	work	-	but	not,	as	the	arguments	of	this section	show,	the	same	work	-	as	their	physical	realizers. 4. Mental Causation for Functionalists The	causal	work	of	properties	consists	in	synchronically	grounding	the dispositions	of	their	bearers;	finding	such	work	for	functional	properties to	do	is	harder	than	showing	that	their	instances	are	diachronic	causes. I'll	now	briefly	recast	the	exclusion	argument	in	terms	of	causal	work. In	Section	2.1,	I	defined	closure	(CC)	as	the	claim	that	every	physical effect	has	a complete, sufficient	physical cause, so that I could later define	'complete'	in	terms	of	my	preferred	conception	of	causal	work: put simply, a complete, sufficient	physical cause	of some	event is a sufficient	cause	of	it	whose	physical	properties	ground	all	the	relevant dispositions.	Think	again	of	a	vase	broken	by	the	impact	of	a	hammer. Since	dispositions	manifest	reciprocally,	we	must	include	in	the	cause the	intrinsic	physical	properties	of	the	vase	itself,	as	well	as	those	of the	hammer,	since	the	former	do	some	of	the	causal	work	required	if the	hammer	is	to	break	it.	Closure	implies	that	the	physical	properties of	hammer	and	vase	ground	both	the	hammer's	disposition	to	break that	kind	of	vase,	and	the	vase's	disposition	to	be	broken	by	that	kind of	hammer.	A	physical	cause	can	be	sufficient	for	some	effect	without being	complete.	Suppose	emergent	downwards	causation	is	possible, whereby a supervenient property-instance emerges from a physical base property-instance, but contributes novel causal powers not grounded	by its	physical	base.	Given the sufficiency	of the	physical base	for	the	emergent	property,	the	effects	of	emergent	powers	have sufficient	physical	causes,	by	transitivity	of	sufficiency;	but	they	don't have	complete	physical	causes.53 53. As	I	understand	it,	(CC)	claims	not	only	that	physical	effects	have	sufficient physical	causes,	but	also	that	the	properties	that	ground	such	causal	relations are	physical.	So	understood,	(CC)	is	about	both	diachronic	causation	(causal david	yates Functionalism and the Metaphysics of Causal Exclusion philosophers'	imprint – 17 – vol.	12,	no.	13	(july	2012) being	a	set	of	possible	conditions	{B1',	...	,Bn'}	such	that	were	the	sheet in	any	of	the	Bi'	and	a	force	of	1N	were	applied,	it	would	flex	by	1cm. If the intersection	of these two	sets is	empty, the	mechanism	won't work.	When	designing	a	mechanism,	we	maximise the intersection set	and	make	sure	it	corresponds	to	the	conditions	under	which	we want the	mechanism to	work. This is	why it	matters not only that, but also how, the dispositions of the components are realized.	My mousetrap	has	DM	because:	(1)	the	components	have	D1–D3;	(2)	the components	have	a	certain	spatiotemporal	structure;	(3)	D1–D3	have a	non-empty	intersection	set	of	background	conditions.	Call	(1)–(3) the	dispositional structure	of the	mousetrap.	Such	structures	typically involve components which are themselves mechanisms, and have their dispositional properties in virtue of their own dispositional structures. As in the example of the hammer and vase in Section 3.2, the properties that ground	DM thereby ground	potential causal relations.	The	mousetrap's	having	DM	consists	in	its	having	intrinsic properties	-	its dispositional structure	-	in virtue of which there's a	range	of	possible	conditions	under	which,	were	a	mouse	to	sit	on the copper sheet, it would be shocked.	What grounds DM thereby grounds	potential	difference-making	causal	relations:	whether	or	not the	mouse	steps	on	the	sheet	makes	a	difference	to	whether	or	not it's	shocked. An obvious rejoinder:	Why isn't it the physical properties of its components that do the causal	work of grounding the dispositions of	a	mechanism?	Reply: It is!	The	causal	powers	of	a	mechanism	are grounded in the fundamental	physical	properties	of its	components. However,	I	deny	that	this	leaves	no	causal	work	for	functional	properties to	do.	In	fact,	I	claim	that	the	grounding	of	a	mechanism's	dispositions by	the	basic	physical	properties	of	its	components	is	secured	only	by the transitivity	of	grounding,	and the fact that	such	dispositions	are grounded in the dispositional properties of its components. Think again	of	the	mousetrap,	and	focus	on	the	copper	sheet,	and	the	physical properties	of	the	sheet	in	virtue	of	which	it	has	D2.	Suppose	the	copper sheet	breaks	and	I	need	to	replace	it	but	have	only	a	thick,	inflexible copper	sheet,	and	set the	sheet in	a	housing	so that the	unattached end	of	the	negative	wire	is	1cm	away	from	the	sheet.	The	components of	my	mechanism	have	the	following	dispositions:	(D1)	the	battery	is disposed	to	send	a	current	of	(1,000,000/R)A	through	a	conductor	of resistance	R	connected	across its	terminals;	(D2)	the	copper	sheet is disposed	to	flex	by	1cm	when	a	force	of	1N	or	greater	is	applied;	(D3) the	wire	is	disposed	to	conduct	a	current	of	(V/10)A	when	a	potential difference of V is applied to it. The mechanism as a whole	-	my mousetrap	-	is disposed to shock mice of mass greater than 100g when	they	sit	on	the	copper	sheet.	Label	this	disposition	DM.	A	mouse of	mass	200g	sits	on	the	copper	sheet,	meeting	the	stimulus	condition of	the	disposition	of	the	sheet	to	flex	by	1cm,	bringing	it	into	contact with	the	wire.	This	in	turn	stimulates	the	reciprocal	dispositions	of	the battery and	wire, sending a current of 100,000A through the sheet, which	shocks	the	mouse.	The	importance	of	structure	should	be	clear. Were	the	negative	wire	not	located	1cm	below	the	copper	sheet,	the sheet's	manifesting its	disposition to	flex	by 1cm	when	an	object	of mass	greater	than	100g	rests	on	it	would	not	trigger	the	dispositions of the other components. The way the components are structured enables the	manifestation of one disposition to be the stimulus of another.	Of	course	not	every	mechanism	is	structured	in	such	a	linear way, but I needn't consider	more complex cases to	make	my point. The entity that has	DM is the	mousetrap itself:	DM isn't identical to any	disposition	that	can	be	attributed	to the individual	components, even	though	its	manifestation	on	some	occasion	is	constituted	by	the structured	manifestations	of	the	dispositions	of	the	components. Now	consider:	which	properties	do	the	causal	work	of	grounding DM? A key element of my proposal is that DM is grounded in the dispositions of the mousetrap's components, together with their spatiotemporal	structure.	According	to	(DISP),	the	battery's	having	D1 consists	in	there	being	a	set	of	possible	background	conditions	{B1,	... ,Bn},	such	that	if	the	battery	were	in	any	of	the	Bi	and	a	conductor	of resistance	R	were	connected	to	its	terminals,	it	would	conduct	a	current of (1,000,000/R)A. The copper sheet's having D2 consists in there david	yates Functionalism and the Metaphysics of Causal Exclusion philosophers'	imprint – 18 – vol.	12,	no.	13	(july	2012) over	particulars	(including	mechanisms),	and	D	over	dispositions,	we may	define	proximal	grounding	as	follows: (PG) X's having P proximally grounds	X's having	D iff (i) X's	having	P	grounds	X's	having	D, (ii) there is	no	P' such	that:	(a)	X	has	P',	and	(b)	X's	having	P	grounds	X's having	P',	and	(c)	X's	having	P'	grounds	X's	having	D. Intuitively,	proximal	grounding is	grounding	without intermediaries. My mousetrap has many levels of mechanism: the battery, for instance , is a mechanism, which is disposed to send a current of (1,000,000/R)A	through	a	conductor	of	resistance	R	connected	to	its terminals,	in	virtue	of	its	dispositional	structure	-	being	composed	of an	anode	and	cathode,	separated	by	an	electrolyte,	say.	The	same	goes for	the	copper	sheet,	which	is	disposed	to	flex	by	1cm	when	a	force	of	1N is	applied	in	virtue	of	the	way	its	atoms	are	arranged,	their	dispositions to	exert	certain	forces	on	their	neighbours,	and	so	forth.	My	mousetrap has	dispositional	structures	at	lower	levels	of	mechanism	than	the	one I've	been	discussing	so	far,	which	don't	proximally,	but	distally,	ground its	power	to	shock	mice: (DG) X's having P distally grounds	X's having	D iff (i)	X's having	P	grounds	X's	having	D,	and	(ii)	¬(X's	having	P proximally	grounds	X's	having	D). Grounding simpliciter, construed as either proximally or distally grounding	a	disposition,	is	transitive.	Proximal	grounding	is	intransitive, because by definition if a proximally grounds b and b proximally grounds	c,	then	a	distally	grounds	c;	distal	grounding	is	transitive.	The basic physical properties of a	mechanism at best	distally ground its characteristic	dispositions.	The	role	of	fundamental	physical	properties is	to	proximally	ground	the	powers	of	fundamental	physical	particles. Such	particles	combine	into	mechanisms	(atoms)	which	have	certain characteristic	powers	in	virtue	of	their	dispositional	structures.	These in	turn	combine	into	molecules,	chemical	compounds,	cells,	and	so	on all	the	way	up.	The	fundamental	properties	of	my	mousetrap	distally aluminium	sheet	to	hand.	What	I	must	do,	if	I	want	my	mousetrap	to continue	working, is to	file the	sheet to	a thickness	such that it too flexes	by	1cm	when	a	force	of	1N	is	applied.	Granting	for	argument's sake that a suitably thin sheet of aluminium also has negligible resistance,	this	example	shows	that	what's	important	when	it	comes	to grounding	DM	is	that	the	components	are	appropriately	structured	and have D1–D3 (realized so that their background conditions overlap). Holding	the	mousetrap's	other	components	fixed,	and	removing	the copper sheet, what	we	must do to get it working again is install a component	of	negligible	resistance	with	D2.	Put	differently:	in	virtue of	its	intrinsic	nature,	the	copper	sheet	has	D2,	and	in	virtue	of	having D2 it's capable,	when	placed in	appropriate structural relations	with the	other	components,	of	completing	the	mechanism.	The	causal	work that	the	physical	properties	of	our	replacement	sheet	must	do	in	order to partially ground	DM is to ground	D2, the	having	of	which	makes it	possible	for	the	sheet	to	form	part	of	a	dispositional	structure	that constitutively	explains	why	the	mousetrap	has	DM. 4.2. Proximal and distal grounding The	physical	properties	of	components	in	a	mechanism	do	the	causal work	of	grounding	the	dispositions	of	those	components,	which	then ground those	of the	mechanism.	The	same is true	even	at the level of	fundamental	physics.	An	electron	orbits	a	proton	in	the	hydrogen atom	due to the	dispositional structure	of electron	and	proton.	The physical	properties	of	electrons	and	protons	ground	the	dispositions of the hydrogen atom, by grounding the reciprocal dispositions of electron and proton to attract each other. It's unlikely that the dispositions grounded by fundamental properties such as charge are	multiply realizable. It remains true, however, that fundamental particles combine into more complex mechanisms in virtue of dispositions that they	have in virtue	of their fundamental properties. Assuming	the	notion	of	grounding	to	be	sufficiently	well	understood, we	can	distinguish	two	kinds	of	grounding:	proximal	and	distal.	Where P	and	P'	range	over	properties	(including	dispositional	structures),	X david	yates Functionalism and the Metaphysics of Causal Exclusion philosophers'	imprint – 19 – vol.	12,	no.	13	(july	2012) grounded in both functional properties and their realizers; what's incoherent	is	the	stronger	claim	that	the	former	inherit	the	causal	work of the latter. Indeed, given upwards causation,	when	basic physical properties distally ground a power via functional intermediaries, it	makes	more sense to say that the	physical properties inherit this component	of their causal	work from the functional	properties that proximally	ground	it. 4.3. Upwards Causation and the Mental In order to save functionalist mental properties from the threat of elimination,	we	need	to	find	novel	causal	work	for	them	to	do.	They can't	do	the	same	causal	work	as	their	realizers,	because	they	are	the causal	work	their	realizers	do.	We	are	now	in	a	position	to	find	such	work for	functional	mental	properties	to	do.55	Mental	properties	proximally ground agent-level dispositions not proximally grounded in agents' physical	properties.	They	are	distally	so	grounded,	but this	depends on	the	transitivity	of	grounding	and	the	fact	that	such	dispositions	are proximally	grounded	in	the	mental.	Suppose	for	the	sake	of	argument that	the	ambient	temperature	comes	in	two	flavours:	cold	and	warm. I have the following	mental properties: (i) I	want to	be	neither too hot	nor	too	cold,	(ii)	I	want	to	go	outside,	(iii)	I	believe	that	if	it's	cold outside,	then	if	I	go	outside	I'll	be	too	cold	unless	I	dress	warmly,	(iv) I	believe	that if it's	warm	outside, then if I	go	outside I'll	be too	hot unless	I	don't	dress	warmly.	Given	functionalism,	(i)–(iv)	are	(clusters of) dispositions. For instance, (i) is	-	inter alia	-	the disposition to dress	warmly	if	I	have	states	(ii)	and	(iii)	and	believe	it's	cold	outside. What	I	don't	yet	know	is	whether	it's	cold	or	warm:	I've	only	just	got	up and	haven't	yet	had	my	coffee,	which	comes	before	opening	the	door to	check	the	temperature.	Being	a	comparatively	normal,	rational	agent with	properly	functioning	senses,	I'm	disposed	to	believe	that	it's	cold outside	when	it is	cold;	ditto	warm.	These	states	combine	to	ground the	following	agent-level	dispositions:	(a)	I'm	disposed	to	dress	warmly 55.	What	follows	isn't	intended	as	an	exhaustive	account	of	the	causal	novelty	of such	properties. ground	its	power	to	shock	mice,	which	leaves	plenty	of	causal	work left	for	the	functional	properties	of	its	components	to	do	-	proximally grounding this	power.	Proximal	and	distal	grounds	occupy	different places	in	a	hierarchy	of	grounding	relations	through	which	the	causal influence	of	fundamental	physics	extends	upwards	to	medium-sized dry goods. This doesn't involve causal closure violations, because there's	no	pressure	at	all	to	read	the	notion	of	causal	work	implicit	in (CC)	in	terms	of	proximal	grounding.	Indeed,	read	in	this	way,	(CC) is false, for there are many dispositional structures between basic physics	and the	powers	of	ordinary	physical	particulars.	Conversely, if	we	take	(CC)	to	imply	that	the	powers	of	ordinary	things	-	agents, engines, aeroplanes, batteries, bananas	-	to bring about certain physical	effects	are	grounded	in	their	fundamental	physical	properties, we	must read 'grounded' as "distally grounded". Far from precluding the causal novelty of functional properties, (CC) actually requires it. Functional properties at a specific level of mechanism are causally novel	because	they	occupy	a	unique	place	in	hierarchy	of	dispositional structures,	without	which	basic	physical	properties	could	ground	only the	powers	of	basic	physical	particulars. Upwards	causation	may	initially	strike	the	reader	as	similar	to	the kind of over-determination strategy I rejected in Section 3.4. There, I argued that it's incoherent to suppose that functional properties inherit	the	causal	work	their	realizers	do,	because	they	are	at	least	part of	that	work.	Since	I	hold	that	functional	properties	proximally	ground dispositions that are distally grounded in the physical, however, I must accept that some causal	work is, in a sense, over-determined. For	upwards causation to	work, there	must	be	dispositions that are grounded	simpliciter	(but	not	proximally)	in	both	functional	properties and	their	basic	physical	realizers,	so	grounding	simpliciter	is	sometimes over-determined. This doesn't undermine my previous arguments against	over-determination,	because	it	remains	the	case	if	functional properties simply inherited the causal work of their realizers, they would be self-grounding dispositions, which doesn't make sense. There's	nothing	wrong	with supposing that there	are	causal	powers david	yates Functionalism and the Metaphysics of Causal Exclusion philosophers'	imprint – 20 – vol.	12,	no.	13	(july	2012) of	their	components;	that	such	mechanisms	are	ultimately	grounded in fundamental	physics is	only	possible	at	all	because	of the	way in which dispositions compose. Basic physical properties ground the powers of complex mechanisms by grounding those of their most basic	components;	from	there	on	it's	functional	all	the	way	up. The theory detailed above involves treating mental properties as	properties	of	components	in	psychological	mechanisms.	It	might be objected that mental properties are properties of agents, and are therefore at the same level of mechanism as the agent-level dispositions	I	claim	they	ground.	A	first	rejoinder:	being	properties of	agents	doesn't	preclude	mental	properties	from	grounding	further dispositions	at	the	agential	level.	I	see	no	reason	why	there	shouldn't be	dispositional	structures	in	which	a	single	component	has	a	set	of dispositions	which	constitutively	explain	why	that	very	component has	some	further	disposition.	Still,	that	isn't	how	I	see	functionalist mental properties, nor, arguably, is it	what functionalists ought to say. Functional properties are physically grounded dispositions. If the	physical	realizers	of	functional	properties	are	neural	properties, then it seems the brain states that bear them will also bear any dispositions they	ground.	On	my	account, functional	property	Fi is the	property	of	being	an	x	such	that	there	are	properties	P1,	...	,Pn	in virtue	of	which,	collectively,	a	certain	conjunction	of	subjunctives	is true,	and	x	has	Pi .	Treating	functional	realization	as	a	kind	of	samesubject necessitation is commonplace, and one	which entails that if	Pi is	a	brain	property,	so is	Fi .	But	on	reflection,	why	shouldn't	a property	of	my	brain	also	be	a	property	of	me?	If	I	grow	my	fingernails long,	isn't	it	true	both	that	my	fingers	have	long	nails,	and	that	I	do? One	might wish to insist that mental properties are properties of whole	agents,	and	not	of	any	proper	parts	thereof,	but in	that	case functionalists	must	either	say	the	same	about	their	realizers,	or	else find	an	alternative	to the	standard	quantificational	way	of	defining second-order	properties.	What	functionalists	ought	to	say,	I	submit, is	that	agents	have	mental	properties	in	the	same	derivative	way	that agents have fingernails. Perhaps there's some reason for thinking when	it's	cold	outside,	(b)	I'm	disposed	not	to	dress	warmly	when	it's warm	outside.	Label	these	DC	and	DW	respectively. My	having	DC	consists	in	my	having	intrinsic	properties	in	virtue of	which	there's	a	range	of	nomically	possible	conditions in	which	I would	dress	warmly	if	it	were	cold	outside;	similarly	mutatis mutandis for	DW.	These	conditions,	as	before,	depend	on	those	of	the	grounding dispositions	-	including,	for	example,	that	I'm	not	under	the	influence of	drugs such that if it	were	cold	outside, I	wouldn't	believe it.	The intrinsic	properties	that	ground	DC	and	DW	thereby	ground	potential causal relations. Suppose it's cold, that some relevant background conditions for	DC and	DW	obtain, and I dress	warmly. The fact that it's	cold	is	a	difference-making	cause	of	my	so	dressing.	The	nearest worlds	at	which	it's	cold	will	be	worlds	at	which	I	have	DC	and	relevant background	conditions	obtains,	hence	worlds	at	which	I	dress	warmly. The	nearest	worlds	at	which	it's	not	cold	will	be	worlds	at	which	I	have DW	and	relevant	background	conditions	obtain,	hence	worlds	at	which I don't dress	warmly. The psychological dispositional structure that grounds	DC	and	DW	thereby	grounds	a	range	of	potential	differencemaking causal relations between the ambient temperature and	my attire. This is no philosopher's invention: I really do have DC and DW, in virtue of something like the dispositional structure outlined, and	my attire really is counterfactually correlated	with the ambient temperature.56	Psychology	proximally	grounds	causal	relations	which, since physics grounds psychology, are distally grounded in physics. Since,	by anyone's lights, a	novel causal role is sufficient for robust ontological	commitment,	functional	properties	are	as	non-redundant as	the	properties	of	fundamental	physics.	Mechanisms	at	any	level	have their defining dispositions proximally grounded in the dispositions 56.	Note	that	this	structure	also	grounds	psychological	difference-making	causes. The ambient temperature	makes a difference to the	way I dress because I have	reliable	belief-forming	mechanisms	that	enable	me	to	detect	it.	As	well as	DW,	for	instance,	I	also	have	-	in	virtue	of	the	dispositional	structure	given by	(i)–(iv)	-	the	disposition	to	dress	warmly	if	I	believe	that	it's	cold	outside. My	belief	that	it's	cold	outside	now	will	later	be	a	difference-making	cause	of my	dressing	warmly	before leaving	work,	as	will the	various	other	dispositions	in	the	structure. david	yates Functionalism and the Metaphysics of Causal Exclusion philosophers'	imprint – 21 – vol.	12,	no.	13	(july	2012) dispositions	of fundamental physical particulars are the	only causal powers to	ground.57	Clearly, it's	no	use	arguing that	dispositions	do novel	causal	work	in	proximally	grounding	higher-order	dispositions if	there	aren't	any	higher-order	dispositions	to	ground.	It	seems	that in	order to	show	that there's	causal	work for	any	dispositions to	do, I need to assume the reality of higher-order dispositions, but that's exactly	what's	at	issue. It's	important	to	get	clear	about	the	dialectic	before	proceeding.	On the table is the	claim	that	any	event	we	can	explain in terms	of the manifestation	of	a	higher-order	disposition	can	be	explained	in	terms of	the	structured	manifestations	of	fundamental	physical	dispositions. I assume the reality of agent-level dispositions, and argue that functionalist	mental	properties	are	causally	novel	in	virtue	of	proximally grounding	such	dispositions. If	mental	properties	are	causally	novel, there's no question of their being eliminated, so my strategy aims to	secure	mental	properties	via	novelty	of	synchronic causal work.	But the	objector	doubts the	reality	of	agent-level	dispositions,	and	so	of course won't grant me that mental properties ground them. Nonfundamental	dispositions	lack	diachronic causal-explanatory novelty,	and so	should	themselves	be	eliminated.	Without	such	dispositions,	there's nothing	for	functional	properties	to	ground,	and	therefore	no	upwards causation.	Fundamental	dispositions	secure	their	ontological	status,	if at	all,	not	by	doing	the	causal	work	of	grounding	further	dispositions, but	by	dint	of	their	diachronic	causal-explanatory	role. I	reply	that	Humeans	have	already	shown	how	to	rebut	this	objection: whether	or	not	a	vase	is	fragile	makes	a	difference	to	whether	or	not it	breaks,	but	whether	or	not it	has this	basic	dispositional	structure doesn't. If	any	kind	of	causal	explanation	is	contrastive,	then	higherorder	dispositions	aren't	explanatorily	redundant,	because	they	have	a contrastive	explanatory	role	that	fundamental	dispositions	don't.	If	we 57. Something	like	this	underpins	Merricks'	(2003)	eliminativism	about	ordinary objects.	Any	irreducible	causal	powers	we	might	attribute	to	such	objects	are rendered	otiose	by	the	causal	powers	of	their	ultimate	constituents.	Lacking novel	causal	powers,	the	objects	themselves	should	be	eliminated. that	mental	properties	can't	both	be	properties	of	agents	and their brains,	but	I	don't	see	what	it	could	be. 4.4. Causal exclusion bites back? I	claim	that	the	causal	work	dispositions	do	consists	in	their	grounding dispositions, and thereby causal relations, at higher levels of mechanism.	But	thus	far	I've	said	nothing	to	explain	why	we	should believe there are such dispositions to ground. Given physicalism, it follows that every mechanism has a fundamental dispositional structure, consisting in its	being	composed	of fundamental	physical components	having	certain	dispositions,	and	a	certain	spatiotemporal structure.	The	basic	components	of	each	mechanism	will	have their dispositions in virtue of their fundamental physical properties, and these	dispositions,	together	with	the	way	their	bearers	are	structured, are	sufficient	to	fully	explain	everything	the	mechanism	does.	Suppose a proton and an electron combine, in virtue of the dispositions grounded	in	their	respective	charges,	to	form	a	hydrogen	atom.	Such	an atom	is	a	mechanism,	in	my	sense,	whose	dispositional	structure	-	its being composed	of a suitably	disposed	and structured	electron	and proton pair	-	grounds dispositions such as its being combustible. Suppose a sample of hydrogen combusts on some occasion, under circumstances	C.	The	dispositions	of	the	electron	and	proton,	together with their spatiotemporal relations, are sufficient to explain the sample's	combustion	in	C.	The	same	will	be	true	all	the	way	up.	Given any	mechanism, however complex, we will in principle be able to explain	what	it	does	on	some	occasion	in	terms	of	the	manifestation of	the	dispositions	of	its	fundamental	physical	components,	and	their spatiotemporal	relations. The explanatory adequacy of fundamental dispositions licenses the following objection: (A) we shouldn't posit any dispositions we	don't need in	order to explain	why things	behave the	way they do, and (B) we'll never need to posit higher-order dispositions for explanatory	purposes. If this objection is correct, then fundamental physical	properties	are	the	only	ones	that	do	causal	work,	because	the david	yates Functionalism and the Metaphysics of Causal Exclusion philosophers'	imprint – 22 – vol.	12,	no.	13	(july	2012) objection	gets	the	burden	of	proof	all	wrong:	the	functional	properties the exclusion	argument targets	are higher-order	dispositions.	Those who	run	Kim's	exclusion	argument	against	functional	properties	can't assume	that	functional	properties	don't	exist,	because	that's	what	the argument is supposed to show. And since functional properties are defined in terms of	macro-events, the exclusion argument can't be premised	on	their	non-existence	either. We	can	think	of	the	exclusion	argument	as	a	reductio.	First,	assume that	there	are	functional	properties.	Then	show	that	such	properties can't do causal work, and conclude that they don't exist after all, because if they did, there would be causally redundant properties, which	(AD)	rules	out.	The	argument	therefore	depends	on	the	truth	of the	following	subjunctive: if functional properties existed, there wouldn't be any causal work for them to do. And that's exactly what upwards causation	refutes: if there	are functional	properties, there's	plenty	of causal	work	left	for	them	to	do,	viz.,	proximally	grounding	functional properties at the next level up. If I were arguing that functional properties exist,	this	would	be	bootstrapping,	but	I'm	not,	so	it	isn't.	The diachronic explanatory novelty of functional properties is sufficient to	justify	our	belief	that	they	exist,	so	the	burden	of	proof	rests	with those	who	would	argue	that	they	don't.	Without	tacitly	assuming	that there	are	no	functional	properties,	proponents	of	the	causal	exclusion argument	can't	show	that	functional	properties	have	no	causal	work to	do.	But if they	are	prepared to	assume that functional	properties aren't real, what's the exclusion argument for? Perhaps the reader has	a	nagging	suspicion	that	mental	properties	still	aren't	doing	any essential	causal	work.	Couldn't	the	agent-level	dispositions	of	agents be	grounded	solely	by	properties	of	basic	physics?	What	if	one	agrees with me that agents have agent-level dispositions, but denies the reality	of	mental	properties?	Well,	mental	properties are dispositions (of components in psychological mechanisms, which contribute to grounding the	dispositions	of	agents).	There's	no	obvious reason to allow that there are agent-level functional properties, such as the disposition	to	dress	warmly	when	it's	cold	outside,	but	deny	that	there want	to	explain	why	the	vase	broke	rather	than	not,	it's	no	use	citing	its basic	dispositional	structure	if	we	also	think	that	at	the	closest	possible worlds	where	it	lacks	that	specific	structure,	it	still	breaks.	The	vase's basic dispositional structure	will be required to explain the precise manner of its breaking, but unless contrastive causal explanation is itself dispensable, higher-order dispositions like fragility aren't diachronically redundant. This is of course the "dual explanandum strategy", which can also be employed as a direct response to the causal exclusion problem.58 I don't employ the dual explanandum strategy in this way, because Humean causation isn't sufficient for causal	work, and the	exclusion	problem is	precisely the	problem	of finding	such	work	for	functional	properties	to	do.	My	aim	here	is	to (i) allow for the sake of argument that if higher-order dispositions were diachronically redundant, then we'd have grounds for their elimination,	and	(ii)	employ	the	dual	explanandum	strategy	to	show that they aren't redundant in this sense.	Having a novel differencemaking	role	isn't	sufficient	for	doing	causal	work	(novel	or	otherwise), but	it	is	sufficient	for	the	kind	of	causal-explanatory	relevance	we	need to	block	explanatory	redundancy	arguments.	Similar	arguments	can	be run	to	show	that	macro-properties	in	general	-	whether	dispositional or not	-	aren't explanatorily redundant: striking a vase makes a difference	to	its	shattering	that	a	particular	microphysical realization	of striking	doesn't	make. Exclusion, however, still isn't done biting. All I've done so far is block a redundancy argument to the effect that higher-order dispositions	aren't real. If such	properties	aren't real, I claim, it isn't because	they	lack	diachronic	explanatory	novelty.	It's	another	matter, however,	to	show	that	they	are	real,	and	it	remains	the	case	that	my theory	presupposes	them.	Worse	than	that,	I	need	macro-events	such as	its	being	cold,	dressing	warmly,	etc.	as	the	relata	of	the	differencemaking	causal	relations	that	license	the	claim	that	grounding	higherorder dispositions counts as causal work in the first place. This 58.	Marras	(1998). david	yates Functionalism and the Metaphysics of Causal Exclusion philosophers'	imprint – 23 – vol.	12,	no.	13	(july	2012) culminating in the psychological mechanisms whose functional properties	proximally	ground	those	dispositions.	Fodor	says: 59 So,	then,	why is there anything except physics?	That,	I	think,	is what	is	really	bugging	Kim.	Well,	I	admit	that	I	don't	know why.	I	don't	even	know	how	to	think about	why.	I	expect to	figure	out	why	there	is	anything	except	physics	the	day before I	figure	out	why	there is	anything	at	all,	another (and,	presumably,	related)	metaphysical	conundrum	that I	find	perplexing. I	agree	with	Fodor	that	this	is	what's	bugging	Kim	-	and	Merricks,	and Heil60	-	and	while I share	Fodor's	pessimism	about the	prospects for an	answer,	I	see	no	compelling	argument	for	the	conclusion	that	there isn't	anything	but	physics.	Extant	Humean	responses	to	the	exclusion problem	are,	to	register	my	agreement	with	Kim,	a	free	lunch:61	making a	difference	isn't	sufficient	for	doing	the	kind	of	causal	work	that	causal closure	appears	to	render	the	province	of	fundamental	physics	alone, and the thought that functional	properties	do the same	causal	work as their realizers is incoherent. However, the distinction between proximal	and	distal	grounding,	together	with	the	reality	of	higher-order mechanisms and their characteristic dispositions, enables functional properties	to	pay	for	their	lunch	the	same	way	physical	properties	do. The causal structure	of the	world, in	my	view, is irreducibly layered. There's	no causal exclusion	problem	because there's far	more causal work	to	do,	in	constructing	such	a	world,	than	is	commonly	supposed.62 59. Fodor	(1997)	p.	161. 60.	Merricks	(2003);	Heil	(2003). 61. Kim	(1998),	ch.	3. 62.	This	paper	grew	out	of	a	seminar	at	King's	College	London,	in	which	I	tried to	persuade	Jim	Hopkins	of	the	intractability	of	the	exclusion	problem.	My thanks to Jim for lively and thought-provoking	opposition.	Thanks also to Mahrad	Almotahari,	Phillip	Goff,	Chris	Hughes,	Nick	Jones,	Shalom	Lappin, Mark	Textor,	Raphael	Woolf,	and	two	anonymous	referees.	Based	on	research funded	by	a	British	Academy	Postdoctoral	Fellowship. are functional mental properties. Whatever the current objector's reason	for	doubting	the	existence	of	mental	properties,	it	had	better not	be their	dispositional	nature. If I'm right that	mental	properties form part of a hierarchy of dispositional structures through which basic physical properties ground the powers of agents, then their grounding	roles	are	every	bit	as	important	as	those	of	their	ultimate physical	grounds. As	I	see	it,	there	are	as	many	levels	of	dispositional	properties	as there	are	levels	of	mechanism.	Protons	and	electrons	are	disposed	to form	Hydrogen,	in	virtue	of	their	basic	physical	properties.	Hydrogen has the further disposition to combust under certain circumstances, releasing water and energy. Now suppose we make a combustion engine in	which	Hydrogen is a component	-	the fuel. The engine's having	the	power	to	make	the	vehicle	move	will	depend	inter alia	on the	dispositional	properties	of	Hydrogen,	but	that's	just	to	say	that	the basic	physical	properties	of	the	electrons	and	protons	that	compose	the Hydrogen	in	the	mechanism	distally	ground	the	power	of	the	engine to	make	the	vehicle	move.	Causal	closure	entails	that	all	dispositions are	grounded	in	properties	of	basic	physics,	but	not	that	there	are	no intermediate	dispositions.	Mental	properties,	I	claim,	are	among	those intermediates,	and	so	are	as important to the	workings	of the	agent as	the	combustibility	of	hydrogen	is	to	an	engine	that	burns	it	as	fuel. 4.5. Conclusion We	live	in	a	world	where	all	causal	powers,	hence	all	causal	relations, are	grounded	in	fundamental	physics,	and	therefore	dependent	upon it. This is apt to	make it seem	as though there isn't really anything but	physics. If the	physical is	doing	all the	causal	work,	why	bother with	anything	else?	The	central	contention	of	this	paper	is	that	if	there are	higher-order	causal	powers	to	ground,	then	although	such	powers are distally grounded in the physical, distal grounding isn't all the causal	work	there	is.	Agent-level	dispositions,	for	instance,	are	distally grounded	in	the	physical	through	a	hierarchy	of	nested	mechanisms, david	yates Functionalism and the Metaphysics of Causal Exclusion philosophers'	imprint – 24 – vol.	12,	no.	13	(july	2012) Physicalism",	in	A.	Beckermann,	H.	Flohr,	and	J.	Kim	(eds.)	(1992). Emergence or Reduction? Essays on the Prospects of Nonreductive Physicalism.	Berlin:	De	Gruyter. ---	(1998).	Mind in a Physical World.	MIT	Press. --- (2003). "Blocking Causal Drainage and Other Maintenance Chores with Mental Causation", Philosophy and Phenomenological Research	67,	pp.	151–176. --- (2005). Physicalism, Or Something Near Enough. Princeton University	Press. LePore,	E.,	and	B.	Loewer	(1987).	"Mind	Matters",	Journal of Philosophy 84,	pp.	630–642. Lewis, D. 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