Abstract
This paper argues that a priori justification is, in principle, compatible with naturalism—if the a priori is understood in a way that is free of the inessential properties that, historically, have been associated with the concept. I argue that empirical indefeasibility is essential to the primary notion of the a priori; however, the indefeasibility requirement should be interpreted in such a way that we can be fallibilist about apriori-justified claims. This fallibilist notion of the a priori accords with the naturalist’s commitment to scientific methodology in that it allows for apriori-justified claims to be sensitive to further conceptual developments and the expansion of evidence. The fallibilist apriorist allows that an a priori claim is revisable in only a purely epistemic sense. This modal claim is weaker than what is required for a revisability thesis to establish empiricism, so fallibilist apriorism represents a distinct position.
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Notes
Various different types of naturalism are discussed in Audi (2000), Goldman (1999), and Stroud (1996). Different versions of epistemic naturalism are discussed in Goldman (1994) and Maffie (1990). See Kitcher (1992) for a formulation and critique of the traditional naturalist position in epistemology. See also De Caro and MacArthur (2004) for a collection of recent critical essays on contemporary naturalism.
Quine (1981, pp. 72 and 21), respectively.
By a “non-trivial” form of a priori justification, I mean an a priori justification that cannot be fully explained in terms of analyticity or by stipulative definition.
The rejection of a “first philosophy” is often understood as the denial that philosophy is an autonomous discipline, or equivalently in this context, that philosophy is continuous with science. Empiricism follows from the continuity thesis if it is combined with a strong version of confirmation holism: the seamlessness of the web of belief ensures that all claims are justified in the same way, namely via the coherence of the system as a whole with experience. (Scientific methods may presuppose a priori elements, so empiricism doesn’t follow from the continuity thesis alone.)
The denial that philosophy is an autonomous discipline is a separate and distinct thesis from the denial that it plays a foundational role—in the sense of providing infallible or rationally-irrevisable standards—in inquiry. For further discussion of this issue, see Siegel (1995). If the commitment to scientific method is taken to be sufficient for methodological naturalism, a naturalist might either reject the foundations thesis while upholding the autonomy of philosophy or reject strong confirmation holism (or both). The methodological naturalist would then not be rejecting a priori justification outright, but only claims of its incorrigibility or infallibility.
Naturalists who, following Quine and Putnam, take us to be committed to the existence of numbers (understood as sets) by virtue of the indispensability of mathematics to science will not object to the admission of abstracta per se, but only an endorsement of them absent a theoretical mandate.
This notion of certainty is employed by Bertrand Russell in Human Knowledge (1948).
A definition of absolute certainty would take something like the following form:
There is some associated class of beliefs Z(P) of which P is a member, ∋ CP ↔ ∼◊ (Some member of Z(P) is false).
A criterion for membership in a relevant class Z would then need to be given to identify a class of absolutely certain beliefs. See Christopher Hookway’s recent discussion of fallibilism and the aim of inquiry (Hookway 2007) for discussion of a notion of absolute certainty that is developed along these general lines. See Firth (1967) for a taxonomy and discussion of epistemological uses of ‘certain’, including absolute certainty.
Gauss’ skepticism regarding the a priori status of parallel postulate and his conception of the possibility of alternative geometries is documented in his correspondence with Friedrich Wilhelm Bessel and H.C. Schumacher. The relevant portions of the correspondence are reprinted in Ewald (1996).
In what follows, I am not assuming that propositions have a mode of existence that is independent from the expressions we use to introduce them.
Cf. Chisholm (1977). Chisholm seems to suggest that justification is an autonomous property that some propositions possess independently of our judgment of them.
As Kripke (1980, p. 35) and others have noted, the claim that a particular proposition can be known a priori should not be understood as the claim that it must be known a priori. A reasonable apriorist will want to allow that a person could have empirical evidence for a proposition that can be known a priori. For example, a child just learning to count might combine five objects with seven objects, then count them to acquire evidence that 5 + 7 = 12. But once the relevant concepts have been acquired, 5 + 7 = 12 could be calculated without the aid of objects.
This is Hartry Field’s formulation (Field 1998) of empirical indefeasibility in his discussion of the apriority of logic.
Alleged counterexamples to modus ponens have been put forth by Adams (1975), McGee (1985), and Lycan (1993); and some philosophers have taken the sorites paradoxes to show that modus ponens is not a strictly valid form of inference. (Whether any particular challenge is an empirical challenge is a further question.) Evaluating these challenges would inter alia involve interpreting the role of idealization assumptions in the formalization of deductive rules and settling questions about the topic neutrality of logic.
Albert Casullo (2003, Chap. 3), distinguishes between two notions of fallibility with respect to a priori justification that are sometimes conflated: a notion of fallibility that allows for an apriori-justified belief to be false, and a notion of fallibility according to which a fallibilist belief is defeasible. No entailment between a priori justification and truth is asserted on my modest notion of the a priori, so it is only Casullo’s second sense of fallibility that needs to be considered.
This general understanding of epistemic possibility is found in Peirce, who took epistemic possibility to be our most basic employment of the term. See Peirce’s Collected Papers, Vol. 6, Sect. 367, 1901, and Vol. 5, Sect. 454, 1905. I am grateful to Robert Meyers for bringing the relevant passages in Peirce to my attention.
Pure epistemic possibility as I am defining it corresponds to what Tamar Szabó-Gendler and John Hawthorne characterize as a permissive notion of epistemic possibility. By contrast, a strict account of epistemic possibility would entail metaphysical possibility. An example of a strict notion of epistemic possibility would be the following: P is epistemically possible for S just in case P is metaphysically compossible with all that S knows (Szabó-Gendler and Hawthorne 2002, pp. 3–4).
An additional epistemic use of possibility is the notion of evidential neutrality that Kripke introduced to express the sense in which a necessary a posteriori claim could have turned out to be false. ‘Hesperus’ and ‘Phosphorus’ name one and the same object, so it is not possible that Hesperus ≠ Phosphorus; yet, given the evidence, it could have turned out that Hesperus and Phosphorus were two distinct objects. However, this notion of epistemic possibility does entail a genuine possibility, so it is not pure as defined above. See George Bealer (2002, Sect. 1.3) for a recent discussion of different epistemic notions of possibility. For further discussion of Kripke’s notion of epistemic possibility, see Stephen Yablo (1993, pp. 22–25; 2002).
The epistemic analysis for the possibility expressed by sentences in the indicative mood is defended by DeRose (1991, 1998), Hacking (1967, 1975), G.E. Moore (1962), and Teller (1972). The authors differ in the details. Hacking also identifies a sense in which possibility is epistemic in subjunctive cases: It is logically and perhaps causally possible that I should have been blind by now, but it is not possible that I am blind now, though it is possible that I shall be blind tomorrow. ‘It is possible that I shall be blind tomorrow’ expresses my state of not knowing that I will not be blind tomorrow, but in order for me to have said something true, it must also be genuinely possible for me to be blind tomorrow.
Hacking proposes (but later retracts) an analysis of epistemic possibility according to which a state of affairs is possible if it is not known not to obtain, and no practicable investigations would establish that it does not obtain. Other proposals, e.g. DeRose (1991), appeal to what can be known to solve this problem.
Strictly speaking, the use of a pure epistemic possibility operator requires reference to one or more knowers. When S asserts ⌈It is not known not to be the case that P⌉, S asserts that no contextually-relevant subset of members of his epistemic community, where the contextually-relevant subset may include S, knows that not P at the time of his assertion. Where ‘Γ’ is an epistemic community for S, S asserts a statement of the form ∼(∃x)[(x ∈ Γ) & Kx(∼p)]. For ease of exposition, I will be suppressing reference to both the asserters and the knowers, except when it is important to identify them.
This difficulty is explored in Lehrer and Kim (1990).
The notion of a context of assessment has been introduced recently in connection with a form of contextualism, dubbed ‘relativism’, that takes ‘knows’ to be sensitive to a context of assessment, as opposed to the context of speaker use or the circumstances (e.g. time) of evaluation of a knowledge claim. On a relativist theory of knowledge-attributing sentences, the truth of a statement employing an epistemic modal is relative to a context of evaluation. Different versions of contextual relativism are defended by John MacFarlane (2005a, b), Mark Richard (2004), Andy Egan et al. (2005), and Andy Egan (2007).
It should be pointed out that an apriorist who wanted to retain rational intuition as a source of a priori knowledge could give a naturalistic account of rational intuition itself. A naturalistic construal of rational insight or intuition might characterize it as a (noninferental) judgment of evidentiality with no attendant claim about access to an independent realm of truths. The term “rational insight” thus might be understood only as loose talk meant to describe whatever psychological processes are involved in coming to see an a priori proposition as evident. Both Bonjour (1998, p. 109) and Goldman (1999, p. 12) have noted that rational intuition could be naturalized along these lines.
Establishing the claim that a priori and necessary propositions are coextensive may be a challenge: while it is widely recognized that there are contingently true a priori statements that acquire their a priori status in virtue of choices we make about fixing the references of our terms, some philosophers have argued that there either are or may be deeply contingent a priori statements for which there is no semantic guarantee that some verifying state of affairs actually exists. See, for example, Williamson (1986) and Hawthorne (2002).
This general point is emphasized by both Hartry Field (1998, 2000) and Georges Rey (1993, 2005). Alternatively, if one were to accept Quine’s extreme version of confirmation holism advanced in “Two Dogmas of Empiricism,” all claims would automatically have empirical justification conditions because the web is seamless and the system as a whole is the unit of confirmation. But this extreme version of confirmation holism is implausible, and Quine himself rejects it as early as Word and Object (Quine 1960, p. 13, fn).
A nonclassical logic might be developed for the purpose of modeling an area of discourse that is not immediately and directly amenable to representation in classical logic, either because some class of statements violates an initial idealization assumption of classical logic or because an apparent violation of a logical principle is discovered within a particular subject matter. Free logics, logics of vagueness, and intuitionist logics for mathematics would be examples of the former, and a quantum logic would be an example of the latter. Whether a “special-purpose” logic should count as a revision to our logic may depend on whether it also is being advanced as a general-purpose logic.
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Acknowledgements
This paper began as a talk for SUNY Albany’s Philosophy Department, which I gave in May 2006. I subsequently presented versions of the paper at the British Society for Philosophy of Science Annual Conference and the Joint Session of the Mind Association and Aristotelian Society in July 2007, and to the University of Connecticut Philosophy Department in October 2007. I am grateful to audience members at all the talks, especially JC Beall, Tom Bontly, Octávio Bueno, Alexander Jackson, Michael Lynch, Robert Meyers, and Ron McClamrock, for useful questions and comments. I would like to thank Ken Akiba, Michael Bishop, and an anonymous referee from this journal for helpful comments on a draft of the paper, and Brad Armour-Garb for stimulating discussion. Special thanks are due to Jonathan Adler and Hartry Field for very helpful comments and discussion.
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An erratum to this article can be found at http://dx.doi.org/10.1007/s11098-012-9889-4
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Warenski, L. Naturalism, fallibilism, and the a priori. Philos Stud 142, 403–426 (2009). https://doi.org/10.1007/s11098-007-9194-9
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DOI: https://doi.org/10.1007/s11098-007-9194-9