Conceivability and Epistemic PossibilityAuthor(s): M. Oreste FioccoReviewed work(s):Source: Erkenntnis (1975-), Vol. 67, No. 3 (Nov., 2007), pp. 387-399Published by: SpringerStable URL: http://www.jstor.org/stable/27667940 .Accessed: 08/11/2012 05:23

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Erkenn (2007) 67:387-399

DOI 10.1007/sl0670-007-9057-y

ORIGINAL ARTICLE

Conceivability and Epistemic Possibility

M. Oreste Fiocco

Received: 20 October 2005/ Accepted: 19 May 2007/Published online: 19 July 2007

? Springer Science+Business Media B.V. 2007

Abstract 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 epi

stemic possibility (and the very term 'epistemic possibility') should be eschewed in the context of modal epistemology.

Keywords Epistemic possibility Conceptual possibility Conceivability Two-dimensionalism Modal epistemology

1 Introduction

Modal knowledge is knowledge of a proposition that represents some state of affairs as being metaphysically possible (or impossible), contingent or necessary. The basis of this knowledge is modal reality. There are two opposing views of the nature of

modal reality. On one, modal reality?what must be and what could be?is wholly

M. O. Fiocco (El)

Department of International Studies (Philosophy), The American University of Sharjah, P. O. Box 26666, Sharjah, United Arab Emirates

e-mail: mfiocco@aus.edu

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388 M. O. Fiocco

determined by the conceptual and linguistic practices of conscious beings; on the

other, more robust view, modal reality is independent of the practices of conscious

beings. Regardless of which view one adopts, the notion of conceivability has

traditionally been regarded as crucial to an account of the modal knowledge available to beings with our cognitive capacities. Conceivability is supposed to

provide insight into both possibility and contingency. Thus, the conceivability of a

proposition, p, has been thought to demonstrate or, at least, to provide some

justification for the belief that/7 is (metaphysically1) possible. Moreover, insofar as

the conceivability of p indicates its possibility, the conceivability of p is proof of the

contingency of any true proposition, q, incompatible with p.2

There is, however, no standard explication of conceivability.3 Some attempt to

explicate it in terms of epistemic possibility. This is confusing, for in contemporary

discussions of modal epistemology, there are two independent notions of epistemic

possibility. One notion is the traditional one, based on what is compatible with a

particular subject's knowledge of the world; the other, of more recent currency, is

based on the coherence of concepts. On the more robust view of the nature of modal

reality, neither notion of epistemic possibility is pertinent to modal knowledge. On

the other view, according to which the nature of modal reality is determined by the

practices of conscious beings, only the conceptual notion of epistemic possibility is

pertinent; however, this view of the nature of modal reality is implausible in light of

compelling counterexamples. Hence, the significance of the notion of epistemic

possibility?under either of its interpretations?is dubious in the context of modal

epistemology.

Yet the distinction between the independent notions of epistemic possibility is not insignificant and the animadversions to follow, regarding the appropriate use of

the term 'epistemic possibility', are not idly terminological. Much substantive

philosophical discussion seems to be based on an inadequate appreciation of the

distinctive features of the two notions of epistemic possibility, in particular, discussions of the putative significance and consequences of so-called Two

dimensionalism4 Thus, insufficient care regarding the distinct notions and their

bases can lead to two sorts of difficulty: a gross problem of conflation and a more

subtle problem of obscuring, with semantical issues, the basic incompatibility of

conceivability qua epistemic possibility with what is the predominant view of the

nature of modal reality. Both problems needlessly complicate efforts to develop an

adequate modal epistemology.

1 This qualification is dropped henceforth. It should be assumed that the intended sense of possibility is

metaphysical possibility, unless explicitly noted otherwise. "

The use of propositions in the text above, to characterize modal knowledge and the putative

significance of conceivability to modal epistemology, should not obscure the fact that the present discussion is compatible with a very robust view of the nature of modal reality. One might regard modal

reality as grounded in the natures of things or their essences (see, for example Fine 1994, Lowe 1998,

Oderberg 2001); however, knowledge of such natures and essences is most perspicuously presented and

discussed as propositional.

There have been, though, significant attempts to clarify and elaborate this notion, most notably, van

Cleve (1983), Yablo (1993), Tidman (1994) and Chalmers (2002). For another attempt, which includes

critical discussion of those just cited, see Fiocco 2007. 4

A characterization of this view, and some discussion of it, follow in ? 6 below.

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Conceivability and epistemic possibility 389

2 Two Views of the Nature of Modal Reality

On one view of the nature of modal reality, what must be as it is and what could

have been (or could become) otherwise is wholly determined by the conceptual and

linguistic practices of conscious beings.5 The only modal constraints there are on

the world are those imposed on it by the means conscious beings use to organize and

describe their experiences of it. So, for example, a pure sample of water must be

clear and potable simply because it is part of the concept6 water that it is clear and

potable. Hence, on this view, modal reality has a significant epistemic feature,

namely, that it is entirely accessible and knowable apriori. Furthermore, the

underlying natures of things are irrelevant to what must be as it is and what could be

otherwise.

On the opposing view, modal reality is independent of the conceptual and

linguistic practices of conscious beings.7 Certain features of the world must be as

they are, while others could be otherwise, and this is so in virtue of the nature of the

things that have those features?regardless of how those things are thought of, referred to or described. Modal facts are, in this way, brute. Hence, there are truths

about modal reality that are inaccessible by mere reflection and can only be

discovered by empirical investigation. For instance, although its chemical compo sition is not part of the concept water, on this view, water nevertheless must be H20.

What is knowable only aposteriori?such as the chemical composition of water?is

indispensable to recognizing the modal status of certain features of the world. It is this latter view of modal reality that underlies and motivates Saul Kripke's

discussion in Naming and Necessity. The influence of those lectures, in combination with the plausible realism that inheres in a view that respects the objective nature of

things, makes this the predominant view of the nature of modal reality.

3 Conceivability as Epistemic Possibility

Interest in the notion of conceivability is motivated by the presumption that whether or not a proposition is conceivable indicates whether the state of affairs it represents

The view, or its underlying sentiment, seems to be somewhat ancient and widespread. However, I know of no place where it is explicitly endorsed, so it is difficult to identify its origins or canonical

presentations. Although it undoubtedly has roots that extend further, into medieval discussions of

metaphysics, it was prevalent throughout the middle decades of the 20th century and is certainly

suggested by the work of Quine and Carnap. See, the papers included in Quine (1980, 2006); see, as well,

Carnap (1988) and the papers appended to this edition of the work. The view is operative in the

contemporary work of Jackson and Chalmers. See Jackson (1994, 1998) and Chalmers (1996, 2002). This

last point is revisited in ? 4. 6

One should construe the concept expressed by a term as a set of properties most or all of which are

associated with the referent or extension of that term by any competent user of it. 7

There are many varieties of robust views of the nature of modal reality, that is, views on which modal

reality is not determined by the practices of conscious beings, but rather by the natures of things (or the natures of their counterparts). See, for an indication of this variety, the papers collected in Loux (1979),

among which are now-classic papers on the metaphysics of modality by Robert Adams, David Lewis, Alvin Plantinga, and Robert Stalnaker. See, also, those papers cited in Note 2 above.

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390 M. O. Fiocco

is possible. Consider now an explication of conceivability according to which a

proposition, p, is conceivable to a subject, S, if and only ifp is consistent with what

S knows. On this account, the conceivability of a proposition is determined by its

relation to a certain body of knowledge. It is unpromising, then, that this explication characterizes a feature of a proposition that is capable of providing insight into

modal reality, for regardless of which view of modal reality one adopts, one would

not expect a particular subject's body of knowledge to be relevant to its nature. Even

if modal reality were determined by the conceptual or linguistic practices of

conscious beings, the knowledge or practices of one such being could hardly be

constitutive of this determination. Thus, a notion of conceivability that is relativized to a single subject can hardly provide insight into modal reality.

Nonetheless, this explication does characterize a notion, traditionally known as

epistemic possibility, that determines a legitimate relative status of a proposition. A

proposition, p, (and, secondarily, the state of affairs represented by p) is

epistemically possible, relative to a subject, S, if p is consistent with what S knows

(in the sense that nothing S knows precludes the truth of/?).8 Epistemic possibility must be distinguished from metaphysical possibility (possibility simpliciter)

according to which a proposition, p, is possible if the state of affairs represented

by p could be?not could be as far as one knows, but could be simpliciter. Once this

distinction is made, it is obvious that some epistemically possible propositions, that

is, propositions conceivable in the sense characterized above, are impossible

(necessarily false). Goldbach's conjecture is the proposition that every even number is the sum of

two primes.9 Assuming that for every mathematical proposition, either it or its

negation is determinately true and, if true, represents a necessary state of affairs,

then either Goldbach's conjecture or its negation is necessarily true. The

mathematical proposition that is not true is necessarily false and, hence, represents

an impossible state of affairs. Given the current state of mathematical knowledge,

for any subject, S, both Goldbach's conjecture and its negation are consistent with

what S knows. So some epistemically possible proposition is impossible.

8 This account of epistemic possibility is over-simplified. These simplifications, however, are irrelevant

to the purposes of the present discussion. For thorough and sophisticated discussions of epistemic

possibility see Hacking (1967, 1975); Teller (1972) and DeRose (1991). Hacking (1967) can be regarded as a locus classicus of epistemic possibility. Therein, Hacking carefully defines the notion and traces it

back to G.E. Moore who, in his Commonplace Book, devotes a good deal of attention to it. 9

This is a classic example in the context of discussions of the nature of conceivability and the sense of

this notion relevant to modal knowledge. It has been employed for different purposes. The example is first

discussed by William Kneale (1949: 80) for the purpose of demonstrating that some "conceivable"

propositions are necessarily false and, thus, that the conceivability of a proposition provides no evidence

of its possibility. The example has been revisited, for example in Yablo (1993: 8 ff.), for the purpose of

clarifying the modally relevant notion of conceivability. Yablo argues that the epistemic sense of

conceivable, the sense in which both Goldbach's conjecture and its negation are conceivable, is not the

sense of conceivability relevant to modal knowledge?precisely for those reasons cited by Kneale.

Consideration of Goldbach's conjecture is also familiar from another context, namely, from Kripke (1980: 36-38), where Kripke employs the example to argue that not all necessary truths are known apriori and, hence, that one must distinguish aprioricity from (metaphysical) necessity. See Hirsch (1986: 245) for a caution not to exaggerate the relevance of Goldbach's conjecture and other mathematical examples in this context. The example is also discussed in Worley (2003).

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Conceivability and epistemic possibility 391

Other propositions that are widely taken to illustrate this point are that Hesperus is not Phosphorus and that Cicero is not Tully. A subject, S, might have such little

knowledge of astronomy or Roman history that these propositions are consistent

with what S knows. They are, then, relative to S, epistemically possible. However,

given that 'Hesperus' and 'Phosphorus' are merely two names of a single planet,

Venus, and that 'Cicero' and 'Tully' name a single Roman orator, the propositions

are not metaphysically possible, for they represent states of affairs in which a thing is distinct from itself.

Another, perhaps more contentious, example?but one worth considering,

because it illustrates the distinction between epistemic and metaphysical possibil ities without relying on hackneyed examples and by placing it in the workaday

world, rather than in the realms of mathematics or semantics?is the following: It is

epistemically possible to a subject, S, as he explores alone a campus building the

layout of which he is ignorant, that a hundred ordinary human beings can sit

comfortably in the space actually behind a given door. This proposition, however,

represents an impossible state of affairs because the space behind the door is in fact

a very small janitor's closet.10

These examples confirm that the epistemic possibility of a proposition does not in

itself provide any evidence of the possibility simpliciter of the state of affairs

represented by that proposition. Therefore, this epistemic notion of conceivability is

not the one sought by those who believe that conceivability holds the key to modal

knowledge.11

4 Conceptual Possibility

Although the foregoing notion of epistemic possibility is irrelevant to modal

knowledge, this notion and the locutions used to express it have been employed to

illuminate the natures of knowledge and of evidence and epistemological

skepticism.12 There is, however, another notion of epistemic possibility that has

received much attention in recent discussions of modal knowledge and that is used to explicate an altogether different notion of conceivability. Unfortunately, the

distinction between these two notions of epistemic possibility has in some cases

been neglected.

10 Note that the actual space behind the door could indeed have been bigger, in the sense that had the

world been different, that is, were we in a different world, that space might have been much larger. However, the space actually behind the door could not have been bigger, given that the quantity of space with respect to a particular space is essential to it. This last claim, about one of the essential features of a

given space, seems to me to be obviously true; if a given space had more or less space it would be a

different space?just as if a given length (or number) were greater or lesser it would be a different length (or number). 1 '

Stephen Yablo presents (and rejects) another explication of conceivability in terms of epistemic

possibility: a proposition, p, is conceivable to a subject, S, if and only if the possibility of the state of

affairs represented by p is consistent with what S knows. See Yablo 1993: 20. This notion of

conceivability is even weaker than the epistemic notion considered in the text. Thus, it is no more relevant

to modal epistemology than that notion is. 12

See the references in Note 8 above.

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392 M. O. Fiocco

The contemporary roots of this other notion of epistemic possibility are in

Kripke's lectures, where he discusses "qualitatively identical epistemic situa

tions".13 The initial discussion of such situations occurs in the context of Kripke's effort to diagnose the firm reluctance of many to recognize the necessity of

propositions expressed by a certain sort of identity statement, to wit, those involving

proper names. Kripke concedes, using the example of Venus and two of its names,

that a subject, S, in a context at a moment prior to the identification of the referent of

'Hesperus' with the referent of 'Phosphorus', could have truly asserted "Hesperus

might not be Phosphorus", expressing thereby that for all S knows, the referents of

the two names are distinct.

But Kripke acknowledges that in some cases, such as this one, there is

"something even stronger" than the epistemic possibility (in certain contexts) of the

distinctness of the referents of the two names grounding the sense had by a subject,

S, of the contingency of the identity statement employing the two names. This

"something even stronger" is, Kripke suggests, 5's awareness of the possibility

(simpliciter) of a subject, Sf, being in a "qualitatively identical epistemic situation", that is, a situation that has perceptually the same phenomenal character, as the one

in which S actually comes to grasp the concept expressed by one of two actually co

referential terms and of S' being in a qualitatively identical epistemic situation to the one in which S actually comes to grasp the concept expressed by the other co

referential term, although the two terms do not refer to the same thing. If such situations are possible for a given term, knowledge of what that term

actually refers to is not obtained merely upon grasping the concept it expresses, for that concept determines different things in different possible situations. Conse

quently, on the assumption that it is the nature of the thing to which that term refers

that determines the modal status of any state of affairs represented by a proposition

expressed by means of it, merely grasping the concept expressed by that term cannot

provide one with modal knowledge of any feature of the world. Even without

knowing what such terms refer to, though, one can reflect upon the conceptual

content of the propositions expressed by them and assess whether those propositions are coherent or incoherent. According to Kripke, one mistakenly judges the state of

affairs Hesperus' being Phosphorus to be contingent?when it is in fact necessary?

on the basis of one's assessment that the proposition Hesperus is not Phosphorus is

conceptually coherent.

Despite Kripke's discussion of qualitatively identical epistemic situations, some

are in danger of conflating epistemic possibility, in the sense characterized in the

preceding section, with a sense of possibility grounded in Kripke's account of the

"something even stronger" that guides one when attempting to assess certain

propositions and the modal status of the features of the world they represent, for

13 Kripke (1980: 103-5, 141^-4, 150-53). One should construe two situations as being "qualitatively

identical epistemically" to a subject, if both induce perceptual states having the same phenomenal character, so that there is no sensory evidence provided by either state that could distinguish between

distinct objects in the two situations that have the same appearances.

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Conceivability and epistemic possibility 393

some characterize this later sense as epistemic possibility. On this other sense of

possibility, a proposition, p, is possible, if the concepts expressed by all the terms

employed to express p are compatible, in the sense that the concepts do not preclude one another in such a way as to make one's mundane conceptual capacities balk; in

other words, the concepts form a representation of a state of affairs that is coherently

describable. This notion, therefore, is clearly different from the notion of epistemic

possibility characterized above and so should be given a different name to avoid

needless confusion. It is, for obvious reasons, best called conceptual possibility.

5 Epistemic Possibility versus Conceptual Possibility

Epistemic possibility and conceptual possibility are significantly different in at least

two ways. First of all, the notion of epistemic possibility is relative to a particular

subject (with a specific body of knowledge), but conceptual possibility is not

relative in this way. Assuming concepts are objective, mind-independent entities,

the conceptual possibility of a proposition in no way depends on any particular

person; moreover, insofar as concepts are supposed to be public and not

idiosyncratic, the compatibility of concepts is completely unaffected by what any

particular person happens to know.

Secondly, whereas epistemic possibility has an aposteriori dimension, in that

what aposteriori knowledge a subject has?and comes to have?determines whether

a given proposition is epistemically possible, conceptual possibility lacks this

dimension. Aposteriori knowledge, in general, is completely irrelevant to the

conceptual possibility of a proposition. Furthermore, since this latter sense of

possibility is grounded in the concepts expressed by terms, one who has mastery of

the relevant terms, has all that is required to determine whether a proposition is

conceptually possible; hence, conceptual possibility is a purely apriori matter. A proposition can be conceptually possible without being epistemically possible,

for example, any conceptually coherent proposition incompatible with what one

currently knows (such as the proposition there is now a rocking chair in my office). A proposition can be epistemically possible to a subject, S, without being

conceptually possible, for example, any conceptually incoherent proposition

employing concepts not in S's repertoire (such as the proposition there is an

extended immaterial being, to S, who has undertaken no philosophical study). Therefore, epistemic possibility and conceptual possibility are not only distinct, but

wholly independent modalities.

14 See, for instance, Jackson (1998: 86); Chalmers (2002: 157); Soames (2004). Chalmers also calls this

notion of possibility, based on conceptual coherence, primary possibility. 15

Although he does so for reasons different than those discussed in the text, Stephen Yablo distinguishes, in passing, epistemic possibility from conceptual possibility. See Yablo (2002: 442-3). Yablo is one of

the few philosophers in current discussions of modal epistemology to make this distinction (see also

Yablo 2000: 99ff.). However, in earlier work, Yablo (1993: 22ff.), when discussing Kripke, Yablo

conflates epistemic and conceptual possibility. See Yablo's conceivability^, presented and discussed in

Yablo (1993: ? IX).

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6 Conceivability, Conceptual Possibility and Modal Reality

There are those who gloss conceivability in terms of conceptual possibility and yet state their explication in terms of "epistemic possibility"; that is, they deem a

proposition, p, to be conceivable if and only if it is "epistemically possible", yet mean by "epistemically possible" that the concepts of the terms used to express p cohere in such a way as to not make one's mundane linguistic or conceptual

capacities balk.16 This subversion of the traditional usage of "epistemically

possible" might be dismissed as trivial, an insignificant terminological quibble, if it were not for the fact that much substantive philosophical discussion seems to be

based on it.17

In recent work, Frank Jackson and, independently, David Chalmers develop and

defend (toward different ends) a position committed to three theses: (i) The notion

of conceivability pertinent to modal knowledge should be understood in terms of

"epistemic possibility" (i.e. conceptual possibility), (ii) Conceptual possibility is all

there is to metaphysical possibility. Nevertheless, (iii) there are necessary

aposteriori truths and, thus, some features of the world must be as they are in

virtue of features inaccessible by mere reflection.18

The position based on these theses is perplexing, in that it seems to combine the two incompatible views of the nature of modal reality introduced above: The claim

that conceptual possibility is all there is to metaphysical possibility seems clearly to

commit one to the view that the nature of modal reality is wholly determined by the

conceptual and linguistic practices of conscious beings and yet the claim that there are necessary aposteriori truths seems to commit one no less to the view that there

are truths about modal reality that are determined by the underlying natures of

things and, hence, can only be discovered by empirical investigation. This position seems to enable one to obtain modal knowledge easily, by apriori means?by

merely reflecting on one's concepts?and yet nevertheless be in the position to

discover substantive, aposteriori modal truths about the world or things in

themselves.

The apparent inconsistencies of this position are, in a sense, reconciled via

insights provided by a technical innovation in logic, namely two-dimensional

operators, ones such that the formulae in which they occur have to be evaluated at

16 Or, alternatively, p is "epistemically possible" when p "is not ruled out a priori" (Chalmers 2002:

157). 17

Those who think of conceivability in this way are almost certainly not ignorant of the distinction

between epistemic possibility (in the sense of ? 3 above) and conceptual possibility. Chalmers seems to be

aware of the distinction when, in passing, he cautions one not to confuse his preferred notion of

conceivability to one on which "a statement is conceivable if for all we know it is true" (Chalmers 1996:

66). It is appropriate, then, to wonder about the motivation for ignoring the usage of the term 'epistemic

possibility' in order to use it to express the notion of conceptual possibility (rather than, as one would

expect, epistemic possibility). One explanation, the simplest, is that those who refer to conceptual

possibility as "epistemic possibility" do so because the former notion is illuminated by Kripke's discussion of qualitatively identical epistemic states.

18 See Jackson (1994: 34ff); Jackson (1998: Chap. 3); Chalmers (1996, 2002).

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Conceivability and epistemic possibility 395

two points in a model, rather than at just one.19 Hence, this position in modal

epistemology might be dubbed Two-dimensionalism. I will not examine Two

dimensionalism here.20 I will, however, note that the position is explicitly based on

the view of modal reality according to which its nature is wholly determined by the

conceptual and linguistic practices of conscious beings. The aposteriori modal truths

it recognizes?and this is key to resolving its apparent inconsistencies?are based

on knowledge not of the underlying natures of things, but rather on knowledge of

how words happen to be used.

My present purpose is simply to point out what is, perhaps, perfectly obvious:

despite accommodating a certain kind of aposteriori modal truth, truths regarding to

what one's words happen to refer, Two-dimensionalism is simply incompatible with

the predominant view of the nature of modal reality according to which how things are in themselves ultimately grounds modal truth. Even without discussing the

details of Two-dimensionalism, this should be obvious by its commitment to the

thesis that conceptual possibility is all there is to metaphysical possibility. If there is

no distinction between conceptual possibility and possibility simpliciter, then what

it is for a proposition to represent a possible (simpliciter) state of affairs is simply for that proposition to cohere in such a way as to not make one's mundane

conceptual or linguistic capacities balk; the underlying natures of the things the

proposition represents are irrelevant.

Two-dimensionalism, however, is much discussed by those who accept (or seem

to accept) the predominant view of the nature of modal reality.21 The view is

examined precisely in order to determine whether it and, more specifically, the

notion of conceivability on which it depends, are capable of providing substantive

modal knowledge regarding things in the world (in particular, the mind and the

brain). Clearly, though, the notion of conceivability on which Two-dimensionalism

is based?conceivability qua conceptual possibility?can provide knowledge only of one's concepts and representational capacities. The only truths the view can

accommodate that are more than merely conceptual regard how words happen to be

used, not objects in themselves, independent of language.

I suggest that the interest in Two-dimensionalism, despite its obvious limitations, is spurred, at least in part, simply by use of the term 'epistemic possibility' in its

formulation. Use of this term, in lieu of the more perspicuous 'conceptual

possibility', suggests, not surprisingly, a notion, to wit, traditional epistemic

possibility, to which aposteriori knowledge of objects in themselves and their

19 See Segerberg (1973) for the basic idea and some discussion of its history. The philosophical interest

in such operators was originally stimulated by the observations that they were of use in developing

temporal logic and that they appeared to be necessary to give a proper formal analysis of the semantics of

certain sentences in natural language employing tense and temporal operators. Their use was extended to

modal logic, in part as a result of attempts to formalize the notion of actuality; (See Davies and

Humberstone 1980) the basic idea underlying such operators has also been used to provide a formal

semantic analysis of natural language. (See, for some of the most famous and influential examples of

formal semantic analyses along these lines, the papers on language in Lewis (1983) and Stalnaker

(1999)). 20

I do this is in detail elsewhere. See my "Two-dimensionalism and Modal Reality". 21

For just a few examples in this growing literature, see Stalnaker (2002), Brueckner (2001), and Balog

(1999).

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396 M. O. Fiocco

underlying natures is pertinent. Just as ignorance of the underlying nature of water

would render epistemically possible, in the traditional sense, all claims regarding this nature, ignorance of the underlying nature of mind?whether it be physical or

otherwise?renders epistemically possible all claims regarding this nature. How

ever, the underlying nature of water or mind is irrelevant to the conceptual

possibility of claims about such things; what is relevant is only how such things are

conceived to be.

Therefore, insofar as one accepts that modal reality is determined by the

underlying natures of things, an account of modal knowledge that construes

conceivability in terms of conceptual possibility can provide no insight into modal

reality. If Two-dimensionalism were presented in terms of conceptual possibility, one would see more easily?even immediately?that the view is fundamentally

incompatible with the predominant view of the nature of modal reality. Alas, it is not presented in these terms, at least not by its proponents. Although Two

dimensionalism is sometimes presented in terms of conceptual possibility by its

critics,22 even in these cases, the limitations of the view are not presented directly

(or directly enough, it seems to me). For even when it is recognized that the

modality relevant to evaluating Two-dimensionalism is conceptual possibility, criticism of the view consists in discussion of subtle semantical issues, rather than a

consideration of the views of the nature of modal reality that seems the proper focus

of a putative account of modal knowledge. Such directness, circumventing the

semantical issues, seems appropriate, rather than merely obtuse given that Two

dimensionalism is supposed to provide insight into how the world must be or could

be otherwise.

Critical strategies focusing on semantic issues arise, I submit, from the contexts

in which Two-dimensionalism is presented by Jackson and Chalmers and,

moreover, the basis of conceptual possibility in Kripke's seminal discussion of

qualitatively identical epistemic states. Nevertheless, if one's concerns are

ultimately with an account of modal knowledge?or, even more specifically, with

what modal knowledge reveals about the relationship between mind and body? then, insofar as one accepts the view of modal reality on which it is determined by the natures of things, conceivability qua conceptual possibility and, afortiori, Two

dimensionalism, are irrelevant. Moreover, in the context of modal epistemology, a

consideration of subtle semantic issues is entirely supererogatory.

7 Conclusion

There are two dangers when one is not very careful to mark the distinction between

epistemic possibility and conceptual possibility. There is the indirect danger, discussed above, of changing the focus of modal epistemology from a consideration

of the means of obtaining knowledge of a modal reality independent of conscious

subjects, to a consideration of merely semantic and related conceptual issues. There

22 For example, Stalnaker (2002). But this is not always the case, for see Soames (2004), in which

Soames' critique of Two-dimensionalism is presented in terms of "epistemic possibility".

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Conceivability and epistemic possibility 397

is also the direct danger of simply conflating the independent modalities of

epistemic possibility and conceptual possibility. Either danger needlessly hampers efforts to develop an adequate account of modal knowledge.

For an illustration of the latter danger, consider Sara Worley's gloss on the

notion of conceivability in the context of evaluating David Chalmers' argument for dualism23: "Whether or not something is conceivable for a thinker depends on what the thinker knows or believes, or what concepts or modes of presentation

he has available or is using to think about the situation....'Conceivable' can be

glossed as 'thinkable,' and surely what we are capable of thinking depends on

what concepts we have available, and what we know or do not know."24 This

gloss clearly conflates the notions of epistemic possibility and conceptual

possibility. Therefore, it is of the utmost importance to modal epistemology to separate

these distinct modalities. If one believes that the key to modal knowledge is

conceivability, where this notion is explicated in terms of conceptual possibility, one need only assess the coherence of a proposition in order to determine

whether it represents a possible or impossible or necessary state of affairs. On

this view, access to modal knowledge is easy, but it seems to come too cheaply:

there are many conceptual possibilities that seem intuitively to be impossible, for

example that Hesperus is not Phosphorus, that water is not H20, that Goldbach's

conjecture (or its negation) is true. One can obscure the basic incompatibility of

(I) the view that conceptual possibility is all there is to modal reality with (II) the

view that there are substantive modal claims about the natures of things in

themselves, by introducing semantic issues, thereby muddling the intuitions that

have motivated many to reject the view that how one speaks or conceives of the

world determines what must be or could be otherwise. Such issues, however,

merely complicate the matter of modal epistemology and can do nothing to

reconcile the incompatible.25

Of course, if one believes that the nature of modal reality is wholly determined

by the conceptual and linguistic practices of conscious beings, then it is

appropriate to explicate the notion of conceivability in terms of conceptual

possibility. But if one holds this view, one must forswear any realist inclinations

and with these any ambition to provide insight into the world as it is in itself.

Once one has done this, modal epistemology seems to lose its metaphysical cachet. If one, however, believes that some features of modal reality are

independent of the practices of conscious beings, then an account of conceiv

ability in terms of conceptual possibility is inappropriate (unless one does not

regard conceivability as the key to all modal knowledge). If one holds this latter

view of modal reality and yet believes that the conceivability of a proposition is

indeed an indication of whether the state of affairs represented by that proposition

23 See Chalmers (1996, 2002).

24 Worley (2003: 17).

25 This is evident in Stalnaker (2002), where Stalnaker seems to come to the same conclusion after much

discussion of ultimately irrelevant semantic issues.

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398 M. O. Fiocco

is possible or necessary, one is still in need of an explication of the relevant

notion of conceivability.26

Regardless of one's view of the nature of modal reality, it should be clear that the

traditional notion of epistemic possibility is irrelevant to recognizing its nature.

Therefore, this notion?and the name 'epistemic possibility'?should be eschewed

in the context of modal epistemology and, more particularly, when explicating or

discussing the notion of conceivability.

Acknowledgements I would like to express my deep gratitude to Anthony Brueckner, Jonathan Dancy, Matthew Hanser and Nathan Salmon for very helpful comments on previous drafts of this paper, as well as to the two anonymous referees for Erkenntnis whose insightful comments enabled many improvements to the final version.

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