There is a long tradition in philosophy of using a priori methods to draw conclusions about what is possible and what is necessary, and often in turn to draw conclusions about matters of substantive metaphysics. Arguments like this typically have three steps: first an epistemic claim , from there to a modal claim , and from there to a metaphysical claim.

To what extent and how is conceivability a guide to possibility? This essay explores general philosophical issues raised by this question, and critically surveys responses to it by Descartes, Hume, Kripke and "two-dimensionalists.".

The capacity to represent things to ourselves as possible plays a crucial role both in everyday thinking and in philosophical reasoning; this volume offers much-needed philosophical illumination of conceivability, possibility, and the relations between them.

Famous examples of conceivability arguments include (i) Descartes’ argument for mind-body dualism, (ii) Kripke's ‘modal argument’ against psychophysical identity theory, (iii) Chalmers’ ‘zombie argument’ against materialism, and (iv) modal versions of the ontological argument for theism. In this paper, we show that for any such conceivability argument, C, there is a corresponding ‘mirror argument’, M. M is deductively valid and has a conclusion that contradicts C's conclusion. Hence, a proponent of C—henceforth, a ‘conceivabilist’—can be warranted in holding that (...) C's premises are conjointly true only if she can find fault with one of M's premises. But M's premises are modelled on a pair of C's premises. The same reasoning that supports the latter supports the former. For this reason, a conceivabilist can repudiate M's premises only on pain of severely undermining C's premises. We conclude on this basis that all conceivability arguments, including each of (i)–(iv), are fallacious. (shrink)

This paper was chosen by The Philosopher’s Annual as one of the ten best articles appearing in print in 2000. Reprinted in Volume XXIII of The Philosopher’s Annual. In his very influential book David Chalmers argues that if physicalism is true then every positive truth is a priori entailed by the full physical description – this is called “the a priori entailment thesis – but ascriptions of phenomenal consciousness are not so entailed and he concludes that Physicalism is false. As (...) he puts it, “zombies” are metaphysically possible. I attempt to show that this argument is refuted by considering an analogous argument in the mouth of a zombie. The conclusion of this argument is false so one of the premises is false. I argue at length that this shows that the original conceivability argument also has a false premise and so is invalid. (shrink)

The Humean view that conceivability entails possibility can be criticized via input from cognitive psychology. A mainstream view here has it that there are two candidate codings for mental representations (one of them being, according to some, reducible to the other): the linguistic and the pictorial, the difference between the two consisting in the degree of arbitrariness of the representation relation. If the conceivability of P at issue for Humeans involves the having of a linguistic mental representation, then (...) it is easy to show that we can conceive the impossible, for impossibilities can be represented by meaningful bits of language. If the conceivability of P amounts to the pictorial imaginability of a situation verifying P, then the question is whether the imagination at issue works purely qualitatively, that is, only by phenomenological resemblance with the imagined scenario. If so, the range of situations imaginable in this way is too limited to have a significant role in modal epistemology. If not, imagination will involve some arbitrary labeling component, which turns out to be sufficient for imagining the impossible. And if the relevant imagination is neither linguistic nor pictorial, Humeans will appear to resort to some representational magic, until they come up with a theory of a ‘third code’ for mental representations. (shrink)

In this paper, we argue that ‘Weak Modal Rationalism’, which is the view that ideal primary positive conceivability entails primary metaphysical possibility, is self-defeating. To this end, we outline two reductio arguments against ‘Weak Modal Rationalism’. The first reductio shows that, from supposing that ‘Weak Modal Rationalism’ is true, it follows that conceivability both is and is not conclusive evidence for possibility. The second reductio shows that, from supposing that ‘Weak Modal Rationalism’ is true, it follows that it (...) is possible that ‘Weak Modal Rationalism’ is necessarily false, and hence that ‘Weak Modal Rationalism’ is false. We then argue that adopting a weaker position according to which conceivability is merely prima facie evidence for possibility provides limited protection from our criticism of conceivability arguments. (shrink)

The paper presents a dilemma for both epistemic and non-epistemic versions of conceivability-based accounts of modal knowledge. On the one horn, non-epistemic accounts do not elucidate the essentialist knowledge they would be committed to. On the other, epistemic accounts do not elucidate everyday life de re modal knowledge. In neither case, therefore, do conceivability accounts elucidate de re modal knowledge.

This paper advances the thesis that we can justifiably believe philosophically interesting possibility statements. The first part of the paper critically discusses van Inwagens skeptical arguments while at the same time laying some of the foundation for a positive view. The second part of the paper advances a view of conceivability in terms of imaginability, where imaginging can be propositional, pictorial, or a combination of the two, and argues that conceivability can, and often does, provide us with justified (...) beliefs of what is metaphysically possible. The notion of scenarios is developed, as is an account of how filling out scenarios can uncover a defeater or, in many cases, strengthen the justification for the relevant possibility statement. (shrink)

The notion of conceivability has traditionally been regarded as crucial to an account of modal knowledge. Despite its importance to modal epistemology, there is no received explication of conceivability. One purpose of this paper is to argue that the notion is not fruitfully explicated in terms of the imagination. The most natural way of presenting a notion of conceivability qua imaginability is open to cogent criticism. In order to avoid such criticism, an advocate of the modal insightfulness (...) of the imagination must broaden the idea of what it is to be imaginable. I argue that this required broadening renders the imagination idle . Consequently, I distinguish two different accounts of the evidential basis of modal knowledge and present a more general argument that concludes that the very notion of conceivability should be eschewed in modal epistemology. (shrink)

My aim here is threefold: to show that conceptual facts play a more significant role in justifying explanatory reductions than most of the contributors to the current debate realize; to furnish an account of that role, and to trace the consequences of this account for conceivability arguments about the mind.

This paper challenges the soundness of the two-dimensional conceivability argument against the derivation of phenomenal truths from physical truths in light of a hyperintensional regimentation of the ontology of consciousness. The regimentation demonstrates how ontological dependencies between truths about consciousness and about physics cannot be witnessed by epistemic constraints, when the latter are recorded by the conceivability—i.e., the epistemic possibility—thereof. Generalizations and other aspects of the philosophical significance of the hyperintensional regimentation are further examined.

This paper offers a detailed criticism of different versions of modal scepticism proposed by Van Inwagen and Hawke, and, against these views, attempts to vindicate our reliance on thought experiments in philosophy. More than one different meaning of “ modal scepticism” will be distinguished. Focusing mainly on Hawke’s more detailed view I argue that none of these versions of modal scepticism is compelling, since sceptical conclusions depend on an untenable and, perhaps, incoherent modal epistemology. With a detailed account of modal (...) defeaters at hand I argue that Van Inwagen and Hawke’s scepticism is either groundless, or it leads to boundless and unacceptable modal scepticism. Additionally, I show that Hawke’s conception of analogical modal reasoning is problematic. Either his principle of similarity is arbitrary or it begs the question about modal scepticism. In contrast to Hawke’s restricted view of analogical modal reasoning, I present two examples of analogy-based modal justification of philosophically relevant possibility claims. My criticism of modal scepticism also shows that there is no good reason to insist on a sharp distinction between an unproblematic and a presumably dubious kind of modality. The upshot is that in absence of proper defeaters both Yablo-style conceivability and properly applied analogical reasoning are reliable guides to possibility, and also that modal justification comes in degrees. The proposed framework of defeaters of modal justification as well as the analysed examples of analogical modal reasoning trace out interesting new areas for further discussions. (shrink)

(2014). A Priori Conditionals and the Conceivability of Zombies. Philosophical Papers: Vol. 43, No. 2, pp. 227-253.

In this paper, I argue that, if transcendental arguments are to proceed from premises that are acceptable to the skeptic, the Transcendental Premise, according to which “X is a metaphysically necessary condition for the possibility of Y,” must be grounded in considerations of conceivability and possibility. More explicitly, the Transcendental Premise is based on what Szabó Gendler and Hawthorne call the “conceivability-possibility move.” This “inconceivability-impossibility” move, however, is a problematic argumentative move when advancing transcendental arguments for the following (...) reasons. First, from “S cannot conceive of P” it doesn’t necessarily follow that P is inconceivable. Second, from “P is inconceivable” it doesn’t necessarily follow that P is metaphysically impossible. Third, rather than block skeptical doubts, the conceivability-possibility move introduces skeptical doubts. For these reasons, transcendental arguments fail to deliver on their promise to overcome skeptical doubts. (shrink)

According to haecceitism, some maximal possibilities differ even while they are qualitatively indiscernible. Since haecceitism is a modal thesis, it is typically defended by appeal to conceivability arguments. These arguments require us to conceive of qualitatively indiscernible possibilities that differ only with respect to the identity of the individuals involved. This paper examines a series of conceivability arguments for haecceitism and a variety of anti-haecceitist responses. It concludes that there is no irresistible conceivability argument for haecceitism even (...) while anti-haecceitist responses do come with certain notable commitments. (shrink)

David Chalmers' conceivability argument against physicalism relies on the entailment from a priori conceivability to metaphysical possibility. The a posteriori physicalist rejects this premise, but is consequently committed to psychophysical strong necessities. These don't fit into the Kripkean model of the necessary a posteriori, and they are therefore, according to Chalmers, problematic. But given semantic assumptions that are essential to the conceivability argument, there is reason to believe in microphysical strong necessities. This means that some of Chalmers' (...) criticism is unwarranted, and the rest equally afflicts the dualist. Moreover, given that these assumptions are independently plausible, there's a general case to be made for the existence of strong necessities outside the psychophysical domain. (shrink)

The superassertability theory of truth, inspired by Crispin Wright (1992, 2003), holds that a statement is true if and only if it is superassertable in the following sense: it possesses warrant that cannot be defeated by any improvement of our information. While initially promising, the superassertability theory of truth is vulnerable to a persistent difficulty highlighted by James Van Cleve (1996) and Terrence Horgan (1995) but not properly fleshed out: it is formally illegitimate in a similar sense that unsophisticated epistemic (...) theories of truth are widely acknowledged to be. Sustained analysis reveals that the unrestricted formal legitimacy argument is firmly grounded in first person conceivability evidence. (shrink)

The conceivability argument against physicalism1 starts from the prem- ises that: It is conceivable that I have a zombie-twin, i.e., that there is someone who is physically identical to me and yet who lacks phenomenal con- sciousness; and If it is conceivable that I have a zombie-twin, then it is possible that I have a zombie-twin. These premises entail that physicalism is false, for physicalism is the claim—or can be assumed for our purposes to be the claim2—that.

Wright (In Gendler and Hawthorne (Eds.), Conceivability and possibility, 2002) rejects some dominant responses to Kripke’s modal argument against the mind-body identity theory, and instead he proposes a new response that draws on a certain understanding of counterpossibles. This paper offers some defensive remarks on behalf of Lewis’ objection to that argument, and it argues that Wright’s proposal fails to fully accommodate the conceivability intuitions, and that it is dialectically ineffective.

The notion of conceivability has traditionally been regarded as crucial to an account of modal knowledge. Despite its importance to modal epistemology, there is no received explication of conceivability. In recent discussions, some have attempted to explicate the notion in terms of epistemic possibility. There are, however, two notions of epistemic possibility, a more familiar one and a novel one. I argue that these two notions are independent of one another. Both are irrelevant to an account of modal (...) knowledge on the predominant view of modal reality. Only the novel notion is relevant and apt on the competing view of modal reality; but this latter view is problematic in light of compelling counterexamples. Insufficient care regarding the independent notions of epistemic possibility can lead to two problems: a gross problem of conflation and a more subtle problem of obscuring a crucial fact of modal epistemology. Either problem needlessly hampers efforts to develop an adequate account of modal knowledge. I conclude that the familiar notion of epistemic possibility should be eschewed in the context of modal epistemology. (shrink)

The central recommendation of this article is that philosophers trained in the analytic tradition ought to add the sensibilities and skills of the historian to their methodological toolkit. The value of an historical approach to strictly philosophical matters is illustrated by a case study focussing on the medieval origin of conceivability arguments and contemporary views of modality. It is shown that common metaphilosophical views about the nature of the philosophical enterprise as well as certain inference patterns found in thinkers (...) from Descartes to Chalmers have their origin in the theological concerns of the Scholastics. Since these assumptions and inference patterns are difficult to motivate when shorn of their original theological context, the upshot is that much post-Cartesian philosophy is cast in an altogether unfamiliar, and probably unwelcome, light. The methodological point, however, is that this philosophical gain is born of acquaintance with the history of ideas. (shrink)

Chalmers argues that zombies are possible and that therefore consciousness does not supervene on physical facts, which shows the falsity of materialism. The crucial step in this argument – that zombies are possible – follows from their conceivability and hence depends on assuming that conceivability implies possibility. But while Chalmers’s defense of this assumption – call it the conceivability principle – is the key part of his argument, it has not been well understood. As I see it, (...) Chalmers’s defense of the conceivability principle comes in his response to the so-called objection from a posteriori necessity. The defense aims at showing that there is no gap between conceivability and possibility since no such gap can be generated by necessary a posteriori truths. I will argue that while Chalmers is right to the extent that there is no gap between conceivability and possibility within the standard Kripkean model of a posteriori necessity, his general conclusion is not justified. This is because the conceivability principle might be inconsistent with a posteriori necessity understood in some non-Kripkean way and Chalmers has not shown that no such alternative understanding of a posteriori necessity is available. (shrink)

This paper examines the ramifications of Hume's view of the relation of conceivability to metaphysical possibility. It argues that the limitations Hume places of the representations involved in moves to conceivability to metaphysical possibility preclude any straightforward argument against full-blooded causal realism in Hume from conceivability. Furthermore, our finding certain states of affairs conceivable when they are not metaphysically possible is perfectly compatible with the thrust of the causal realist position.

We often decide whether a state of affairs is possible by trying to mentally depict a scenario where the state in question obtains . These mental acts seem to provide us with an epistemic route to the space of possibilities. The problem this raises is whether conceivability judgments provide justification-conferring grounds for the ensuing possibility-claims . Although the question has a long history, contemporary interest in it was, to a large extent, prompted by Kripke's utilization of modal intuitions in (...) the course of propounding certain influential theses in the philosophy of language and mind. The interest has been given a further boost by the recent two-dimensional approach to the Kripkean framework. In this paper, I begin by providing a detailed examination of a most recent attempt to defend the thesis and argue that it is unsuccessful. This is followed by presenting my own gloss on Kripke's explanation of the illusions of contingency and I close by raising a general problem intended to undermine the prospects for a successful defense of the thesis. (shrink)

In the history of modern philosophy systematic connections were assumed to hold between the modal concepts of logical possibility and necessity and the concept of conceivability. However, in the eyes of many contemporary philosophers, insuperable objections face any attempt to analyze the modal concepts in terms of conceivability. It is important to keep in mind that a philosophical explanation of modality does not have to take the form of a reductive analysis. In this paper I attempt to provide (...) a response-dependent account of the modal concepts in terms of conceivability along the lines of a nonreductive model of explanation. (shrink)

In his very influential book, The Conscious Mind, David Chalmers argues that if physicalism is true then every positive truth is a priori entailed by the full physical description – this is called “the a priori entailment thesis – but ascriptions of phenomenal consciousness are not so entailed and he concludes that Physicalism is false. As he puts it, “zombies” are metaphysically possible. I show that his argument can be refuted by considering an analogous argument in the mouth of a (...) zombie. The conclusion of this argument is false so one of the premises is false. I argue at length that this shows that the original conceivability argument also has a false premise and so is unsound. (shrink)

In addition to conceiving of such imaginary scenarios as those involving philosophical zombies, we may conceive of such things being conceived. Call these higher order conceptions ‘meta-conceptions’. Sorensen (2006) holds that one can entertain a meta-conception without thereby conceiving of the embedded lower-order conception. So it seems that I can meta-conceive possibilities which I cannot conceive. If this is correct, then meta-conceptions provide a counter-example to the claim that possibility entails conceivability. Moreover, some of Sorensen’s discussion suggests the following (...) argument: if the conceivability of some proposition entails its possibility, then the meta-conceivability of some proposition entails its possibility; but we can meta-conceive impossibilities; so conceivability doesn’t entail possibility. In this paper, I’ll argue that one cannot entertain a meta-conception without thereby conceiving of the embedded lower-order conception. And so we can neither meta-conceive impossibilities nor meta-conceive possibilities of which we cannot thereby conceive. (shrink)

Hill and Levine offer alternative explanations of these conceivabilities, concluding that these conceivabilities are thereby defeated as evidence. However, this strategy fails because their explanations generalize to all conceivability judgments concerning phenomenal states. Consequently, one could defend absolutely any theory of phenomenal states against conceivability arguments in just this way. This result conflicts with too many of our common sense beliefs about the evidential value of conceivability with respect to phenomenal states. The general moral is that the (...) application of such principles of explanatory defeat is neither simple nor straightforward. (shrink)

Some time ago I wrote a paper about conceivability and knowledge. An anonymous referee rejected it on the grounds that the result had already been established in a short story by Jorge Luis Borges. Intrigued, I looked for the story but found no mention of it in Louis and Ziche’s extensive bibliography. I spent months consulting archives and electronic records to no avail. I had begun to doubt whether the story even existed when I had the curious good luck (...) to encounter Sir Thomas Browne of Pembroke College, Oxford, who assured me of the piece’s authenticity and introduced me to Brother Christian Rosenkreuz of Invisible College who in turn generously put me into correspondence with Borges himself. The literary defects in what follows reflect not a diminution of Borges’s undoubted power as a storyteller, but merely my limited ability as an amateur translator. Whatever the translation’s literary faults may be, I hope the story’s philosophical interest—i.e., an argument that ideal conceivers have higher-order knowledge of necessary truths—remains. [Trans.]. (shrink)

What can be inferred from the fact that something is, or is not, conceivable? In this paper I argue, contrary to some deflationary remarks in recent literature, that arguments which use such facts as their starting point may have significant philosophical import. I use Strawson's results from the first chapter of "Individuals" in order to show that Galileo's arguments in favor of the distinction between primary and secondary qualities, which are based on premises concerning conceivability, should not be dismissed: (...) they are the first step towards recognizing an important conceptual truth. (shrink)

Conceivability is an important source of our beliefs about what is possible; inconceivability is an important source of our beliefs about what is impossible. What are the connections between the reliability of these sources? If one is reliable, does it follow that the other is also reliable? The central contention of this paper is that suitably qualified the reliability of inconceivability implies the reliability of conceivability, but the reliability of conceivability fails to imply the reliability of inconceivability.

In his Essays on the Intellectual Powers of Man, Thomas Reid offers a barrage of objections to the view, held by David Hume, that conceivability implies possibility. In this paper, I present Reid's first two objections to the ‘maxim of conceivability’ and defend Hume from them. The first objection concerns our ability to understand impossible claims, while the second concerns thoughts about impossible claims (such as, for instance, the thought that they are impossible). Reid's objections have special force (...) against Hume because of his commitment to analyse all operations of the understanding in terms of conception. I argue that these objections fail, on the grounds that they presuppose substantive views about language which we are not warranted in attributing to Hume. Ultimately, Reid's objections help us draw out a set of intertwined issues about the language-mind relationship in Hume. (shrink)

A. Collins once argued that time travel is only imaginable if we relate the "event" out of context. John Hospers argues that it is logically possible for an iron bar to float in water even if it is actually (empirically) impossible. My point in this piece is that Hospers relies on viewing the floating out of context, in Walt Disney fashion; but that is no way to establish any kind of possibility. I also discuss "conceivability", a term frequently used (...) either to clarify logical possibility or to interchange for the same. I argue that it cannot do either. (shrink)

The dissertation addresses the mind-body problem, and in particular, the problem of how to fit phenomenal consciousness into the rest of reality. Phenomenal consciousness---the what it's like feature of experience---can appear to the scientifically inclined philosopher to be deeply mysterious. It is difficult to understand how the swirl of atoms in the void, the oscillation of field values, the firing of synapses, or anything physical can add up to the smells, tastes, feelings, moods, and so forth that comprise our phenomenal (...) experience. There is a series of arguments---the so-called "Conceivability Arguments"---that spells out this puzzlement. If this arguments are successful then there is no place for phenomenal consciousness in a completely physical reality. The main conclusion of this dissertation is that the Conceivability Arguments are all dependent on a flawed premiss, and that therefore these arguments---perhaps the most powerful among anti-physicalist arguments---all fail. ;Conceivability Arguments begin with the premiss that we can conceive of any physical or functional facts obtaining without there being any phenomenal experience at all. This is sometimes expressed by saying that zombies are conceivable. The claim that zombies are conceivable does not have to do with our powers of imagination, or our psychological abilities, but rather with the nature of physical and phenomenal concepts. The reason that zombies are claimed to be conceivable is that each person's thinking about phenomenal properties is completely dependent on her first person acquaintance with her own experience. From this assertion of conceivability it is inferred that zombies are genuinely possible. And this conclusion is incompatible with physicalism as that doctrine is usually understood. ;I argue that these arguments all fail; they are refuted by a master argument that I call "the Zombie Refutation." The reason they fail has to do with the very nature of phenomenal concepts that gives rise to the conceivability of zombies. Because of the special nature of these concepts, the principle underlying the Conceivability Arguments---that principle that links conceivability and possibility---turns out to be self-refuting. Thus, the zombies that the Conceivability Arguments supposedly demonstrate to be possible, return to undermine those very arguments; a fitting revenge. (shrink)

Hume's maxim consists of two principles which are logically independent of each other: (1) whatever is conceivable is possible; and (2) whatever is inconceivable is impossible. Thomas Reid offered several arguments against the former principle, while John Stuart mill argued against the latter. The primary concern of this paper is to examine whether Reid and mill were successful in calling Hume's maxim into question.

The purpose of this article is to defend Hume's claim that whatever is conceivable is possible from a criticism by William Kneale. Kneale argues that although a mathematician can conceive of the falsehood of the Goldbach conjecture, he does not conclude that it is not necessarily true. The author suggests that by taking into account Hume's distinction between intuitive and demonstrative knowledge, a revised version of his claim can be offered which is not open to Kneale's criticism.

David Chalmers’ ‘conceivability’ argument against physicalism is perhaps the most widely discussed and controversial argument in contemporary philosophy of mind. Recently, several thinkers have suggested a novel response to this argument, which employs the ‘powerful qualities’ ontology of properties. In this paper, I argue that this response fails because it presupposes an implausible account of the physical/phenomenal distinction. In the course of establishing this, I discuss the so-called ‘ultimate’ argument for the claim that dispositional properties form the subject matter (...) of physics. I argue that the ultimate argument can be interpreted in a strong or a weak way, and that the strong interpretation is implausible. I argue that this undermines the powerful qualities based response to the conceivability argument. I also argue for a general conclusion: that we should not define ‘the physical’ exclusively in terms of a distinction drawn from ontology. (shrink)

It is widely suspected that arguments from conceivability, at least in some of their more notorious instances, are unsound. However, the reasons for the failure of conceivability arguments are less well agreed upon, and it remains unclear how to distinguish between sound and unsound instances of the form. In this paper I provide an analysis of the form of arguments from conceivability, and use this analysis to diagnose a systematic weakness in the argument form which reveals all (...) its instances to be, roughly, either uninformative or unsound. I illustrate this conclusion through a consideration of David Chalmers. (shrink)

In The Conscious Mind, D. Chalmers appeals to his semantic framework in order to show that conceivability, as employed in his "zombie" argument for dualism , is sufficient for genuine possibility. I criticize this attempt.

The conclusion of this argument entails the falsity of physicalism because, technical details aside, physicalism is or entails the thesis that every psychological truth is entailed by some physical truth. If it is possible that I have a zombie duplicate however, then it is possible that the physical truths are as they are and some psychological truth is different. Hence 3 entails that physicalism is false. The second conceivability argument is one that is almost as famous, though perhaps it (...) is less famous for being a conceivability argument: the perfect actor argument against behaviorism . In a version that is both familiar and relatively clear, it goes like this. (shrink)

Our limited a priori-reasoning skills open a gap between our finding a proposition conceivable and its metaphysical possibility. A prominent strategy for closing this gap is the postulation of ideal conceivers, who suffer from no such limitations. In this paper I argue that, under many, maybe all, plausible unpackings of the notion of ideal conceiver, it is false that ideal negative conceivability entails possibility.