(forthcoming in Philosophical Studies) Hume versus the vulgar on resistance, nisus, and the impression of power Colin Marshall, University of Washington Abstract: In the first Enquiry, Hume takes the experience of exerting force against a solid body to be a key ingredient of the vulgar idea of power, so that the vulgar take that experience to provide us with an impression of power. Hume provides two arguments against the vulgar on this point: the first concerning our other applications of the idea of power and the second concerning whether that experience yields certainty about distinct events. I argue that, even if we accept Hume's conception of the vulgar's approach, neither of Hume's arguments succeeds. The first argument can be resisted either by using the very arguments Hume provides concerning other causal representations or by simply rejecting Hume's strict empiricism. The second argument can be resisted on epistemological grounds: there is no reason to think that an experience of a maximally-strong metaphysical connection would provide a maximally-strong epistemological connection. Unlike some recent neo-Anscombean responses to the second argument, my response does not require challenging Hume's view that causal relations are strictly necessary. Though I do not attempt to translate the resilience of the vulgar view into contemporary terms, the failure of Hume's arguments challenges one of the long-standing motivations for Humean approaches to causation. Keywords: Hume, resistance, causation, touch In Section 7 of the Enquiry Concerning Human Understanding, Hume aims to identify the origin of our idea of "power, force, energy, or necessary connexion" (7.3 – Hume uses these terms interchangeably in this section).1 Guided by his principle that all ideas are copied from impressions (cf. 2.5), Hume ultimately concludes that the idea of power could be derived only from the "customary transition of the imagination from one object to its usual attendant" (7.28), a transition that arises after experience of constant conjunctions of events. A key sub-conclusion in Hume's argument is that in single experiences of events or eventpairs, "we never can, by our utmost scrutiny, discover any thing but one event following another; without being able to comprehend any force or power, by which the cause operates, or any connexion between it and its supposed effect" (7.26).2 Hume's overall argument for this sub-conclusion proceeds by considering and rejecting various candidates for the impression of power that we might be said to encounter in 1 References to passages from the Enquiry are by chapter and paragraph number. References to Hume's Treatise are by book, part, section number, and paragraph number. References to Locke's Essay are by book, chapter, and paragraph number. 2 Some of Hume's readers have taken such statements as implying that he believes there is a secret connection binding events together (so that causation is more than mere regularity), and his negative claim is only that regularity is all we know about the nature of causation (e.g., Strawson 1992). I remain neutral on this issue in what follows. 2 single experiences. Though all the candidate impressions Hume considers have some prima facie plausibility as an impression of power, the case he most explicitly ties to the common way of thinking about causation concerns "the resistance which we meet with in bodies, obliging us frequently to exert our force, and call up all our power" (7.15n.). In a long footnote, Hume argues that while this experience "enters very much into that vulgar, inaccurate idea [of power]," it "can afford no accurate precise idea of power" (ibid.). My aim in what follows is to show that Hume's arguments against the vulgar on this point fail. Before turning to Hume's arguments, four preliminary points: (1) My focus will be on the Enquiry, which contains the most mature statement of Hume's views on causation and is the only place where Hume explicitly attacks this vulgar view. I will touch on some relevant parts of the Treatise at a few points, though. (2) In responding to Hume's arguments, I limit myself to views that Hume would have thought were available to the vulgar. Hume does not provide a detailed account of the vulgar's philosophical views,3 so a certain amount of guesswork will be involved. In general, I will assume that the vulgar accept a naïve view of the world and of perception but, aside from taking experiences of resistance to involve impressions of power, have few specific philosophical commitments. I will also take it as a constraint that the vulgar cannot appeal to counter-intuitive premises unless those premises are also endorsed by Hume himself. It is likely, however, that Hume thinks that some philosophers have been drawn to the vulgar view. Locke is an especially likely target. For in the Essay, Locke states: The Idea of Solidity we receive by our Touch; and it arises from the resistance which we find in Body, to the entrance of any other Body into the Place it possesses... There is no Idea, which we receive more constantly from Sensation, than Solidity. Whether we move, or rest...we always feel something under us, that supports us, and hinders our farther sinking downwards; and the Bodies which we daily handle, make us perceive, that whilst they remain between them, they do by an insurmountable Force; hinder the approach of the parts of our Hands that press them... This of all other, seems the Idea most intimately connected with, and essential to Body. (Essay 2.4.1, my emphases) 3 We do get a number of hints, though, especially in the Treatise. The vulgar "take things according to their first appearance" (Treatise 1.3.12.5). This means, at least in part, that the vulgar take both qualities like bulk and solidity and qualities like color and heat to "have a distinct continu'd existence" apart from our perceptions (Treatise 1.4.2.12). Hume also says that it is part of the popular way of thinking, and natural to imagine, that "we feel the solidity of bodies, and need but touch any object in order to perceive this quality" (Treatise 1.4.4.12). In causal matters, the vulgar "imagine they perceive a connexion betwixt such objects as they have found constantly found united together" (Treatise 1.4.3.9). 3 Note that Locke states that, even when we rest (and so are not performing any intentional action), we feel things resisting our movement (e.g., the floor hindering our sinking). Locke describes this experience in recognizably causal terms, calling its object a force.4 Later in the Essay, Locke claims that we understand the connection between solidity and impulse: Our Knowledge in all these Enquiries, reaches very little farther than our experience. Indeed, some very few of the primary Qualities have a necessary dependence, and visible connexion with one another, as Figure necessary supposes Extension, receiving or communicating Motion by impulse, supposes Solidity. (Essay 4.3.14) So, on this point at least, Hume's opposition to the vulgar is also an opposition to Locke. (3) Another important candidate Hume considers for the impression of power is the experience of one's own agency. This is also a view Locke endorses (cf. Essay 2.21.4) and several philosophers have recently defended this view against Hume's arguments.5 Though, as we'll see, the arguments I'm concerned with do make reference to some sort of experience of agency, that is not my main interest here.6 Finally, (4) I want to emphasize that whether Hume's arguments against the vulgar succeed is not merely a question of historical interest. For it is plausible that this part of Hume's views continues to exert influence in contemporary metaphysics. This is illustrated by the number of contemporary metaphysicians who directly address Hume's arguments (see below for specific references). Another telling example is Jonathan Schaffer's Stanford Encyclopedia of Philosophy article on contemporary views of causation, where Schaffer writes that someone might reasonably dismiss "a naive (pre-Humean) conception of causation as requiring some sort of metaphysical push or 'oomph'".7 Schaffer does not 4 Despite calling solidity a force, Locke does not explicitly discuss solidity in his chapter on active and passive powers (Essay 2.21). This may be because he thinks of active powers as what allows a substance to initiate a causal chain, and of passive powers as a substance's mere capacity for being changed (cf. Essay 2.21.2). Solidity would then be somewhere between an active and passive power. It does not itself initiate any causal chains, and so is less than an active power, but it does contribute to the continuation of causal chains (e.g., by causing objects to bounce off each other), and so is more than a mere capacity for change. 5 Among others: Mumford and Anjum 2011, Schrenk 2014. 6 Though we differ on some key points, the previous commentator whose approach is closest to my own, especially in responding to Hume's second argument, is Evan Fales (in Fales 1990). Fales' important discussion, while occasionally referenced, is under-appreciated: Armstrong 1997 mentions Fales' view, but leaves out several key pieces. Despite the significant affinities between their views and his, there is no mention of Fales in Mumford and Anjum 2011. 7 Schaffer 2008. Schaffer later cites several post-Humean metaphysicians who side with the vulgar view, some of whom I mention below. 4 explicitly cite Hume's footnote, but it is hard to see what else he has in mind. The footnote is the main place where Hume argues against something like a push being involved in causal relations. It would be a non-trivial task to translate the vulgar view, Hume's arguments, or the implications of the failure of Hume's arguments into contemporary terms, and I can only hint at the results of that translation here.8 1. Hume's footnote Hume presents two arguments against the vulgar view in a footnote in Section 7, which I quote here in full: It may be pretended, that the resistance which we meet with in bodies, obliging us frequently to exert our force, and call up all our power, this gives us the idea of force and power. It is this nisus or strong endeavour, of which we are conscious, that is the original impression from which this idea is copied. But, first, we attribute power to a vast number of objects, where we never can suppose this resistance or exertion of force to take place; to the Supreme Being, who never meets with any resistance; to the mind in its command over its ideas and limbs, in common thinking and motion, where the effect follows immediately upon the will, without any exertion or summoning up of force; to inanimate matter, which is not capable of this sentiment. Secondly, This sentiment of an endeavour to overcome resistance has no known connexion with any event: What follows it, we know by experience; but could not know it a priori. It must, however, be confessed, that the animal nisus which we experience, though it can afford no accurate precise idea of power, enters very much into that vulgar, inaccurate idea, which is formed of it. (7.15n.)9 At first pass, it is not entirely clear which candidate impression for the idea of power Hume is considering here. The first sentence of the footnote suggests that the impression in question is an impression of something primarily in external bodies, namely resistance. The second sentence, however, seems to state that the impression is of something primarily in us and 8 A key step in such translation, I believe, would be understanding Hume's talk of impressions in terms of something like Russellian acquaintance (as opposed to understanding them in terms of a weaker notion of perceptual representation). Though this has only suggestive value, it's worth noting that Hume talks of acquaintance at various points in the Enquiry, and seems to treat having an impression of something as sufficient for acquaintance (cf. 2.8, 9.2). Note that Hume seems confident that everyone will accept his basic ontology of the mental in terms of impressions and ideas (cf. 2.1-3). 9 Hume returns to nisus in the last footnote of Section 7 of the Enquiry, but does not add anything significant to his argument: "No animal can put external bodies in motion without the sentiment of a nisus or endeavour; and every animal has a sentiment or feeling from the stroke or blow of an external object, that is in motion. These sensations, which are merely animal, and from which we can a priori draw no inference, we are apt to transfer to inanimate objects, and to suppose, that they have some such feelings" (7.29n.). Hume's apparently pejorative use of 'animal' here is somewhat uncharacteristic (cf. Section 9 of the Enquiry). For discussion of the hint of an argument here, see Fales 1990, 14-15. 5 related to intentional action, namely "nisus or strong endeavour."10 Most of the remainder of the footnote accords with the second sentence, though Hume continues to vacillate a bit (e.g., in the third sentence: "this resistance or exertion of force... the Supreme Being, who never meets with any resistance"). Regardless, we should take the focus to be on the overall experience of endeavoring against the resistance of an external body, since Hume's conclusion requires that there is no impression of force or power anywhere in that experience.11 Focusing on this overall experience, one might think that Hume is implying that we experience resistance from external bodies only when endeavoring to do something. That would surely be a mistake on Hume's part. As the above passage from Locke emphasized, we can experience bodies pushing against us even when we are at rest. A more careful reading of the passage suggests that Hume made room for this, though: his initial claim is only that the resistance in question frequently leads to action on our part. So we should also consider the bare experience of feeling bodies press against us, even when we aren't endeavoring to do anything in response. To succeed against the vulgar, Hume's arguments need to show that in no case do we have an impression of power. I consider each argument in turn. Like Hume, I will use talk of power, force, and causation interchangeably. 2. Hume's first argument Once again, Hume's first argument runs as follows: we attribute power to a vast number of objects, where we never can suppose this resistance or exertion of force to take place; to the Supreme Being, who never meets with any resistance; to the mind in its command over its ideas and limbs, in common thinking and motion, where the effect follows immediately upon the will, without any exertion or summoning up of force; to inanimate matter, which is not capable of this sentiment. (7.15n.) 10 Given the ultimate aim of Hume's argument, it is puzzling that he initially describes this endeavoring as "exert[ing] our force" and "call[ing] up our power." If we aim to read Hume charitably, we should take these phrases merely as superficial accommodations to the vulgar way of speaking. 11 As Joshua Wood (manuscript) shows, Hume's concern with nisus has important ties to Berkeley and Leibniz – in fact, his use of the term 'animal nisus' probably derives from Berkeley's De Motu. Wood argues that, at least as far as Leibniz's notion of nisus is concerned (which may well have been another of Hume's targets), Hume is wrong to think nisus has any important tie to physical exertion. 6 The core idea of the argument seems to be that if the experience in question were the origin of the idea of power, then something similar to that experience would have to be present in any application of the idea of power. But since nothing like those impressions (of "resistance or exertion of force") is present in "a vast number of objects" to which we apply the idea of power, that experience must not be the origin of the idea.12 The "something similar" and "nothing like" here are crucial, for Hume of course allows that we can apply ideas to things that are somewhat different from those we experienced before. How to draw the line between what is 'somewhat different' and what is 'nothing like' is not obvious. This makes way for one line of response to Hume's first argument. That is, we could insist that we do think of something similar to the experience in question in the other cases Hume considers, e.g., an asymmetric dependence between particulars.13 This response, though, appeals to the sort of abstraction Hume is skeptical about (cf. 12.15, Treatise 1.1.7), and would require sophisticated philosophical defense. To defend the vulgar, we should consider other responses. A more serious concern is that Hume himself has given the vulgar the resources they need to reply. Provided they are willing to accept some of Hume's other conclusions, the vulgar needn't be moved by Hume's argument here. More specifically: they might grant that there is an inaccurate idea of power that is applied to certain cases where there is nothing like the original impression in question, but maintain that the accurate idea of force would not be so applied. For not only does Hume rely on a distinction between accurate and inaccurate ideas, but he also provides particular reasons for thinking that there is something inaccurate about our ways of thinking about causation in the three cases he lists: (i) the Supreme Being, (ii) our intentional thoughts and movements, and (iii) inanimate matter. With (i): We know Hume is suspicious about the coherence of the idea of a supreme being, especially concerning that being's causal powers (cf. 11.15, 11.26). The vulgar (perhaps with an eye towards mysticism) might well accept that we have no adequate idea of causation that applies to God. With (ii): Hume himself has just argued in the main text that we have no impression of "power or energy in the will" (7.11). The vulgar presumably would have initially disagreed, but if they now accept Hume's earlier argument, they need not now have to demonstrate that 12 Materialists might be tempted to shrug off at least the part of the argument concerning God, but I think that would be too quick (Markus Schrenk, for instance, sets aside the 'Supreme Being' part of the argument on grounds of methodological atheism (Schrenk, 2014)). Even if we do not accept the existence of God, we might still need an account of our idea of causation that makes sense of how it is so frequently applied to God. 13 Evan Fales takes an approach along these lines (Fales 1990, 13-14). 7 what they take to be the impression of power can be found there. Finally, with (iii): Hume's vacillation between talk of resistance and talk of exertion makes room for the vulgar to claim that the impression of resistance alone is sufficient for the idea of power, provided they agree with Locke in holding that we can experience the force of solidity in bodies even when we are at rest. With that, it would be open to the vulgar to say that the accurate idea of force applies not just to cases of us endeavoring against resistance, but also to relations between pieces of inanimate matter like billiard balls, despite the latter not being capable of the sentiment of exertion.14 In a different vein, the vulgar (unlike Locke) might resist Hume's argument by rejecting his principle that all ideas are copied from impressions. That is, the vulgar could simply say that while the experience in question does involve an impression of power, that impression need not explain all of our thoughts about powers. 15 3. Hume's second argument Hume's statement of the second argument is very brief: "This sentiment of an endeavour to overcome resistance has no known connexion with any event: What follows it, we know by experience; but could not know it a priori." The brevity is due to the argument's being of a type that Hume has made several times up to this point in Section 7. The key to this type of argument is the following principle, which Hume states explicitly earlier in the section: From the first appearance of an object, we never can conjecture what effect will result from it. But were the power or energy of any cause discoverable by the mind, we could foresee the effect, even without [further] experience; and might, at first, pronounce with certainty concerning it, by the mere dint of thought and reasoning (7.7). 14 On this last point, cf. Massin 2009, 578 (who lists others who have made related suggestions). In the Treatise, Hume argues that we can make no sense of the resistance we experience in bodies resembling a quality in mindindependent bodies themselves (Treatise 1.4.4). But his grounds there are quite general, and extend to our experience of shape, motion, etc. Those general skeptical arguments are independent of (and not obviously consistent with) the arguments of 7.15n. 15 In fact, Leibniz and Kant may have had such a view, namely, that we experience force at least as directly as we do shape, but that we do not derive our causal concepts from such experiences. See Leibniz's New Essays on Human Understanding, 124 and Kant's Metaphysical Foundations of Natural Science 4:510. I discuss this view in Marshall (manuscript). 8 The idea of the second argument seems to be this: if the endeavor to overcome resistance contained an impression of power, then the our first experience of that type alone would let us (reasonably) "foresee" or "pronounce with certainty" what was going to happen next.16 Hume seems right, however, that our first experience of endeavoring to overcome resistance would not enable us to pronounce with certainty what will happen next. Sometimes Hume argues for this kind of claim with a kind of thought-experiment: he asks us to imagine someone encountering objects for the first time (e.g., the case of Adam at 4.6), and claims that it is clear that in such cases that the person would be unable to infer either the causes or effects of perceived events. The significance or reliability of such thought-experiments might be doubted, though, so it is important that Hume has an alternative line of argument here (cf. 4.10). This alternative line runs as follows: even after accumulated experience, we cannot foresee future events with certainty. As we push open a heavy door, we cannot be certain whether it will continue to move, stop, fall off its hinges, or even suddenly change direction and start pushing us backwards. Yet it seems plausible that accumulated experience could hardly put us in a worse predictive position than we were in with our first experiences. Since we have less than perfect certainty even with the benefit of multiple experiences of the relevant type, we can infer that we lacked such certainty on the first such experience. Unless the vulgar are willing to claim such certainty, their only approach to resisting Hume's argument would be to provide reasons for rejecting his principle connecting predictive certainty with the impression of force. The most obvious way to reject that principle would be to attack the metaphysical view of causation that underlies it. More specifically: in these arguments Hume assumes that powers (causes) necessitate their effects. Given that maximally-strong metaphysical connection, he supposes that an impression of power would have to yield a maximally-strong epistemological connection, namely, 16 Three complications: First, it is not obvious what Hume takes the relation to be between psychological certainty and epistemic justification. I take it Hume thinks they go together in this case, but the general issue is complicated (for an in-depth discussion, see Loeb 2002). Second: it is worth asking whether Hume's principle concerns only inferences to future events (foresight), or extends more widely. Despite the wording of the above passage, Hume's use of the principle suggests a wider reading: at 4.6, he emphasizes that Adam would not be able to draw inferences about either the effects or the causes of the things he first encounters (see also the quotations below concerning Hume's reasons for interest in causal relations). Third, though Hume does not say this, it seems essential to his argument that it must be the intrinsic nature of the candidate impression that would put us in a position to foresee the effect. So if we are, say, hard-wired from birth to expect stationary objects to start moving upon contact with moving objects, that alone would not be enough to challenge Hume's views. The expectation must be based in the intrinsic nature of the conscious experience. 9 foreseeing the effect with certainty. Not surprisingly, then, the approach previous respondents to Hume have taken is to deny that causes necessitate their effect. Elizabeth Anscombe denied the necessity of causation by arguing that we have a notion of one thing determining another that does not require thought of necessity – a line which a number of more recent philosophers have been drawn to in discussing Hume.17 In his critique of Hume's argument, Evan Fales develops this approach in two steps.18 First, Fales denies that causal connections should be understood as anything like necessary logical connections. Second, he claims that while, for any effect, there is some total cause that (in some weaker sense of "necessitates") necessitates it, the individual causes that make up that total cause are not sufficient for the effect, so that one could legitimately have an impression of a (non-total) cause without having certainty about the effect. There are problems with challenging the underlying conception of causation in Hume's argument, however. For Hume seems to treat it as a definitional truth (or in his terms: a relation of ideas) that causes necessitate their effect, so these replies invite the charge of changing the topic. This is hardly a stipulation on his part: many of the early moderns thought of causation in terms of strictly necessary connection. Moreover, insofar as we are interested in how the vulgar might respond to Hume, pursuing this line would require showing that the vulgar do not think of power and causation in terms of strict necessity – a difficult task at best. So it would be better if we could find grounds for rejecting Hume's principle without challenging the underlying notion of causation. I think that Hume's argument can indeed be resisted on different grounds. The rest of the section explains how, in three stages. First, I identify epistemological motivations for significantly weakening the crucial principle, motivations that the vulgar could accept. Second, I point out that the weakened principle is one that Hume himself, with good reason, 17 Anscombe 1971. With Hume's argument in view, David Armstrong advances a broadly similar line: "Hume's target... was the old rationalist conception of causation where causation was assumed to be necessary in the way that, say, Euclidean geometrical theorems were assumed to be necessary. He was certainly right to argue that we perceive no such necessity in causal sequences. But here is a position that Hume does not consider. It is the position that, in favourable situations, singular causal relations are perceived without any perception of the necessity of the relation.... They need involve no perception of necessity, nor need there be any necessity" (Armstrong 1997, 211). See also Massin 2009 (who also insists on distinguishing forces from causes), Schrenk 2010, Mumford and Anjum 2011, and Schrenk 2014. Mumford and Anjum also seem to think that a view that makes causes simultaneous with their effects has some force against Hume's argument (Mumford and Anjum 2011, Chapter 9), but that seems to me to put too much weight on Hume occasional talk of foresight (see the previous note). 18 Fales 1990, Ch. 1. See also Schrenk 2011, 597. 10 sometimes tends towards. Finally, with the weakened principle in place, I argue that the vulgar are safe from Hume's argument. 3.1 Epistemological grounds for weakening Hume's principle As we saw, Hume's second argument hinges on the principle that an impression of force would allow one to infer the effect with certainty. There are, it turns out, purely epistemological grounds for rejecting Hume's principle, grounds that are available even if we grant that the metaphysical connection between causes and effects is maximally-strong. We can identify these grounds by developing the second step of Fales' approach described above, leaving aside the first step. As an analogy, consider one way the vulgar might explain our experience of opaque objects having volume. Sticking to Hume's language of impressions and taking a naïve view of perception, we might say that at any moment we have impressions only of the surfaces of external, opaque objects. For example, we might have an impression of a rock's surface, break it into pieces, and then have impressions of the surfaces of the resulting pieces. Each experienced surface, we might then say, is only a fragment of volume, and our full idea of volume comes only from combining them imaginatively (perhaps using imagined similar impressions to fill in the gaps). The case of our own body might be slightly different. With our own body, perhaps we can have individual (proprioceptive) impressions of more than just surfaces in space, but even these will be incomplete: our impressions of our bodies are neutral on many details (e.g., where exactly the empty cavities in our lungs are). Given these limitations, if our idea of an external or internal body filling space is based on our impressions, then that idea will have to be the result of combining very many impressions (including many merely imagined ones). An all-seeing being might be able to have an impression of an opaque body's filling space at a single moment, but that is not possible for us. Given our limitations, we would expect that no single impression be able to fully reveal to us opaque bodies' occupation of space. Despite that, there is no deep sense in which this feature of reality is hidden from us. One could of course tell other empiricist stories about our ideas of objects' having volume. I claim only that the above is an account the vulgar (as Hume conceived them) could have told. But now consider a parallel story for powers. I lean against a door, and it opens. On the naïve view of powers, this was (let's say) a matter of the physical powers of my body overcoming certain resistant powers of the door, and necessitating its opening. Yet the 11 interplay of these powers occurs in a large region of space (including the area of the hinges, the other side of the door, etc.). In contrast, my impressions of the resistance of the door concern only some sub-regions of that space. An all-feeling being who could feel all the relevant regions of space at once would have been able to foresee with certainty that and how the door was about to open, we might think,19 but we are not such beings. Given the limitations of our tactile impressions, we see only fragments of the interplay of forces that necessitate the effect. If a full impression of necessitating power would yield predictive certainty, then a fragmentary impression would yield only a predictive suggestion. The central thought in this way of resisting Hume's principle is this: we'd only expect an impression of a maximally-strong metaphysical connection to yield a maximally-strong epistemological connection if that impression were of the whole of the former. But there's no reason to think the vulgar take themselves to be all-sensing in those cases where they would claim to have an impression, and only with such all-sensing capacities would we expect the impression to provide the maximally-strong epistemological connection. In other words, Hume's strong principle applies only to epistemically idealized subjects, and so we should adopt a weaker principle for epistemically limited subjects like ourselves. 3.2 Hume's acceptance of the weakened principle Evidence that this line of thought is correct comes from Hume himself. For even though he typically demands certainty as a necessary condition for having an impression of power, Hume often suggests a much weaker condition. Reconsider the first sentence of the above quote concerning prediction and experience of causation: "From the first appearance of an object, we never can conjecture what effect will result from it" (7.7). Here, Hume does not mention certainty. Rather, his claim is merely that an experience of force would allow us to conjecture what effect will result. Presumably, 'conjecture' here means more than 'speculate' – it seems to mean something like 'reasonably expect some effect over others.' We find this more moderate tone elsewhere in Section 7: In reality, there is no part of matter, that does ever, by its sensible qualities, discover any power or energy, or give us ground to imagine, that it could produce any thing, or be followed by any other object, which we could denominate its effect. Solidity, extension, motion; these 19 The vulgar, I take it, assume the uniformity of nature. If an all-feeling being were convinced of Hume's way of connecting conceivability and possibility, it might have less than certainty if it imagined the possibility of the door simply vanishing, or having new repulsive force appear from nowhere. 12 qualities are all complete in themselves, and never point out any other event which may result from them. (7.8) Here, Hume's language suggests that the discovery of force need only yield a "ground to imagine" some other object, or "point out" a certain result. All this sounds like a much lower bar than certainty. Similarly in the statement of Hume's negative conclusion, quoted above: "we never can, by our utmost scrutiny, discover any thing but one event following another; without being able to comprehend any force or power, by which the cause operates, or any connexion between it and its supposed effect" (7.26). Hume's inference seems to be: because we only ever experience one event following another, we never comprehend (presumably: have an impression of) power. Of course, strictly speaking, those statements are consistent with the stronger principle stated above, but Hume's emphasis here suggests that we might have grounds for claiming an impression of power if we had anything more than mere succession. An impression of an event that merely suggested another might be enough. To drive the point home, consider one more passage, from Section 4 (where the challenge concerning causation is introduced): "the effect is totally different from the cause, and consequently can never be discovered in it. Motion in the second billiard-ball is a quite distinct event from motion in the first; nor is there any thing in the one to suggest the smallest hint of the other" (4.9). 20 By contrast, Hume never claims that, on the metaphysical side, causes might relate to their effects in a less than maximally-strong way (cf. the definition of 'power' in the final footnote of Section 7).21 Taking a step back, we can see that such statements are not mere accidents. Suggestions and small hints would be enough for the role causal relations play in Hume's system. The primary reason Hume is so concerned with the relation is stated in Section 4 of the Enquiry: "All reasonings concerning matter of fact seem to be founded on the relation of 20 A referee for Phil Studies suggested that these passages could be read as Hume just emphasizing how far away we are from having any impression of power. A possible analogy: the statement "You haven't proven I'm guilty – you don't have a single shred of evidence!" does not imply that a single shred of evidence would be sufficient for proving guilt. I grant that this is a possible reading of at least 4.9, though the relation between inference and causation in Hume's system (discussed in the next paragraph) makes me think that Hume took his argument to require the denial of even mere-suggestion-yielding impressions. 21 My suggestion here should not be confused with the 'New Hume' proposal that Hume thought causal powers (in some thick sense of 'causal') were real but beyond our understanding (for one important discussion, see Millican 2009). On the view I've described, Hume would be entertaining only the possibility that causal connections might be knowable in the same way that the volumes of three-dimensional opaque objects are: by accumulating partial views. Whether Hume ultimately allows there to be 'deep' and robustly real causal powers is another question. 13 Cause and Effect. By means of that relation alone can we go beyond the evidence of our memory and senses" (4.4). Hume cares about causal relations, in the first instance, because they seem to be how we are able to (justifiably) form beliefs about things beyond presently perceived and remembered ones. But, as Hume was well aware, one can go beyond the memory and senses with less than certainty.22 So a suggestive impression of power could be enough to explain our (less than certain) inferences to the unobserved. 3.3 How the vulgar can resist Hume's second argument So far, I've argued that the vulgar could offer epistemological grounds for weakening the key principle of Hume's second argument, and that Hume at times seems to limit himself to the weaker principle. On that weakened principle, it is not a necessary condition of having an impression of power that one foresee some effect with certainty. What's necessary is only that the impression in question alone (setting aside the effects of custom) suggest, point to, or give a hint about something distinct. If that is right, then Hume's argument requires that the experience of resistance does not have even such merely suggestive power. This, however, makes Hume's task more difficult. When the issue was foresight with certainty, Hume was able to argue that, since we lack such certainty even with the benefit of accumulated experience (and so, with the additional influence of custom), the experience alone is surely not sufficient for certainty. But, with our accumulated experience, all of us surely do find experiences of resistance at least suggestive of certain further events (e.g., feeling the solid floor beneath me increases my confidence that I won't be sinking downwards). So Hume's argument requires somehow bracketing the effects of custom and isolating the experiences of resistance. The only argumentative tool Hume has for such a claim about the isolated experiences are the sort of thought-experiments I mentioned earlier: imagining what it would be like for a newly-created human to have a certain type of experience for the first time.23 We can 22 For this reason, I set aside Hume's apparent emphasis on knowledge in the penultimate sentence of the footnote. As far as I can tell, Hume never considers the possibility that a single experience might give us grounds for a less than certain inference (contra Fales 1990, 24), despite his giving a clear place to probabilistic inference in our thoughts about matters of fact (the topic of Section 6 of the Enquiry). 23 No empirical study will be of direct help here, for reasons noted above. The issue is the suggestive force (if any) of the experience of resistance alone. Even if we could isolate newborns' responses to feelings of pressure from random movements, there would be no obvious way of telling whether those responses were based on the intrinsic qualities of the experience itself or were merely reflexive. 14 presume that Hume's view is that, if we imagine a newly-created human having such an experience, we will see that she would not find the experience of resistance even suggestive of anything else. If that is now the crucial point in Hume's argument, then, I think, the vulgar have a decisive response: either Hume is simply wrong, and a newly-created person would find such experiences suggestive in the relevant way, or we have no reason to trust the imaginative results of this kind of thought-experiment. To make this response, all the vulgar need is a thought-experiment that (1) seems to show that a newly-created person would find the experience suggestive and (2) yields that result with at least as much plausibility as Hume's thought-experiments yield the results he claims they do. For if we find a thought-experiment that supports the vulgar view and is even close to Hume's thought-experiments in terms of plausibility, then we'll have found reason to distrust the reliability of this argumentative approach. Here is such a thought-experiment. Imagine a subject who has never before experienced anything like pressure, but is nonetheless able to consider possible motions. Say that this subject feels his body being pressed lightly from the left and being pressed heavily from the right.24 Now say that this subject wonders whether, given those feelings of pressure alone, it is more likely that his body will start moving left (away from the heavier pressure) or right (away from the lighter pressure). If we are willing to play along with this kind of Humean imaginative exercise, it seems plausible that the very experience of the difference in the two sensations, on its first occurrence, would give the subject suggestive (if less than certain) grounds for thinking it is more likely that he will start moving left than that he will start moving right. In fact, it is hard to know how to even characterize the difference in the feelings of levels of pressure except in such predictive terms. Differences in intensity of pressure sensations seem to simply be differences in how strongly they suggest movements in certain directions. Yet if this line of thought is correct, then experiences of pressure can indeed 'point out' distinct things or events, albeit with less than certainty. Such imaginative phenomenology is, to be sure, an odd basis for an argument. One might well be skeptical of our ability to imagine a single experience of force (or of anything else) in absolute isolation. Our current experiences might be infused with theory and with 24 Fales offers a more elaborate case: a communicative but otherwise new-to-the-world subject whose head is immobilized and then struck with a blow (Fales 1990, 23-24). Fales also contends that the subject could accurately infer the speed and direction at which his head would have moved had his head not been immobilized. Fales' case seems to me to involve unnecessary complications (including the counterfactual nature of the inference), and Fales is more confident about the reliability of such thought-experiments than I am, but the core intuition his case and mine aim for is the same. 15 past experience (and so, perhaps, Humean custom) in a way that makes them radically unlike our first experiences. In addition, even if there is some resemblance between our current experiences and our first experiences, our imaginative abilities might not be up to the task of sorting out the right dimensions of resemblance. Yet these worries cut both ways. Hume needs such optimism about the imagination in order to claim that the "sentiment of an endeavour to overcome resistance has no known connexion with any event: What follows it, we know by experience; but could not know it a priori." Without assuming some ability to assess what isolated experiences give us grounds for, Hume's second argument turns into a dogmatic insistence. Alternatively, say that we feel initially confident about our imaginative abilities, and that the Humeans among us honestly insist that when they imagine such a subject they see quite clearly that he would have no grounds for the relevant sort of inferences. Nonetheless, there are at least some people who find the opposite conclusion plausible (at the minimum: Fales, me, and perhaps Locke), so such disagreement provides grounds for distrusting these imaginative abilities. Given the various idealizations needed for the case, there are no obvious empirical ways of supporting the claim that the experiences of resistance are not even suggestive of certain movements. If so, then Hume's argument again loses out, for we then lack any non-question-begging argument for distrusting the vulgar idea of power. 4. Conclusion A committed Humean will hardly regard the above as a decisive argument against the Humean view. A decisive argument would require decisively demonstrating that the impression of resistance, uninfluenced by custom, yields an idea of power. For the reasons given above, I doubt this can be done. In addition, a committed Humean can easily tell a story about why we might find the vulgar view tempting. She could maintain, for instance, that it only seems like experience of resistance points out certain results over others because we are projecting our experience-based expectations from past experiences of resistance. I think this sort of psychological hypothesis has some plausibility in cases of visual perception of causation,25 though it seems less plausible to me in the tactile case. Either way, whether we should pursue such psychological explanation hinges largely on how well-motivated the Humean view about the origin of our idea of causation is in the first place. I hope to have 25 Cf. Siegel 2008. 16 shown that its epistemological motivations are not as strong as is often thought. If the vulgar idea of power is safe from Hume's arguments, then contemporary Humeans may need to reconsider the idea of causation in terms of pushes and 'oomphs.'26 26 For comments and discussions, I'm grateful to Tristram McPherson, John Morrison, Mike Raven, Markus Schrenk, Jonathan Simon, Cass Weller, Joshua Wood, and the participants of the 2013 Australian Metaphysics Conference. 17 Works cited Anscombe, G.E.M. 1975 (originally 1971). "Causality and determination." In E. Sosa (ed.), Causation and Conditionals. London: Oxford University Press. Fales, Evan. 1990. Causation and Universals. London: Routledge. Hume, David. 1999 (originally 1748). An Enquiry Concerning Human Understanding, Tom Beauchamp (ed.). Oxford: Oxford University Press. -2000. A Treatise of Human Nature, David Fate Norton and Mary J. Norton (eds.). Oxford: Oxford University Press. Leibniz, Gottfield. 1996 (originally 1765). New Essays on Human Understanding. Peter Remnant and Jonathan Bennett (trans.). Cambridge: Cambridge University Press. Locke, John. 1979 (originally 1689). Essay Concerning Human Understanding. Peter H. Nidditch (ed.). Oxford: Oxford University Press. Loeb, Louis E. 2002. Stability and Justification in Hume's Treatise. Oxford: Oxford University Press. Marshall, Colin. Manuscript. "Kant on force and impenetrability." Massin, Olivier. 2009. "The metaphysics of forces." dialectica 63:4, 555-589. Millican, Peter. 2009. "Hume, causal realism, and causal science." Mind 118:471, 647-712. Mumford, Stephen and Anjum, Rani Lill. 2011. Getting Causes from Powers. Oxford: Oxford University Press. Schaffer, Jonathan. 2008. "The Metaphysics of Causation", The Stanford Encyclopedia of Philosophy (Fall 2008 Edition), Edward N. Zalta (ed.), URL = <http://plato.stanford.edu/archives/fall2008/entries/causation-metaphysics/>. Schrenk, M. 2014. 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