Abstract
In this paper it is argued that sensitivity theory suffers from a fatal defect. Sensitivity theory is often glossed as: (1) S knows that p only if S would not believe that p if p were false. As Nozick showed in his pioneering work on sensitivity theory, this formulation needs to be supplemented by a further counterfactual condition: (2) S knows that p only if S would believe p if p were true. Nozick further showed that the theory needs a qualification on the method used to form the belief. However, when these complications are spelled out in detail, it becomes clear that the two counterfactuals are in irresolvable tension. To jibe with the externalist intuitions that motivate sensitivity theory in the first place, (1) needs a fine-grained grouping of belief-formation methods, but (2) needs coarse-grained grouping. It is therefore suggested that sensitivity theory is in dire straits: either its proponents need to provide a workable principle of method individuation or they must retrench and give up their claims to providing sufficient conditions for knowledge.
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Notes
Cf. Nozick (1981, p. 177).
I will use the following abbreviations throughout the paper: “Bp” for “S believes that p,” and “x → y” for the subjunctive conditional “If x were the case, then y would be the case.”
Of course, a compromise could be made by giving yet a third reading to the subjunctive conditional. Say “x → y” is true just in case the closest non-actual-x-world is a y-world. To my knowledge only Michael Levin has proposed this rather obvious reading (forthcoming: “Sensitivity Training”).
Cf. Nozick (1981, p. 179).
As Quine’s famous slogan puts it, “There is no entity without identity” (1981, p. 102), so if we are to countenance doxastic methods, we need a clear principle of individuation.
For instance, he rewords (iii′) as “If p weren’t true and S were to use M to arrive at a belief whether (or not) p, then S wouldn’t believe, via M, that p” (1981, p. 179). M occurs in both the antecedent and the consequent of the subjunctive conditional here. Need it?
“A perceptual equivalent of an actual state of affairs is a possible state of affairs that would produce the same, or a sufficiently similar, perceptual experience” (Goldman 2005, p. 93). If not for the “sufficiently similar” rider, this would be a very helpful definition. The whole problem is how similar is similar enough.
Note that Goldman is working with reliabilism rather than sensitivity theory. The two are contrapositive cousins (reliabilism says Bp → p and ~Bp → ~p where sensitivity theory says p → Bp and ~p → ~Bp). Although the counterfactual conditional cannot be validly contraposed, results that apply to one theory can often be applied with at most minor modifications to the other.
In his forthcoming “Sensitivity Training”, Levin identifies a fallback position for reliabilism. He says that “a method [M] for forming [the belief that p] is trivializing (for p) if [M] cannot be used unless p; Moore’s method [seeing a hand], for instance, trivializes.” Perhaps (iii′′′′) and (vi′′) both give the right results if we individuate methods trivially? One obvious problem with trivializing methods is that they completely beg the question against skepticism. That aside, a decision to use trivializing methods does not give us a definition for R. Trivializing methods are compatible with m 1 and m 2 in the above examples being tokens of the same method type (since in all such cases p is true at both @ and W), but they are also compatible with m 1 and m 2 being different. The question of trivializers is thus orthogonal to our problem.
References
Goldman, A. (2005). Discrimination and perceptual knowledge. In S. Bernecker & F. Dretske (Eds.), Knowledge (pp. 86–102). Oxford: Oxford University Press.
Harman, G. (1973). Thought. Princeton: Princeton University Press.
Levin, M. Sensitivity training. Erkenntnis (forthcoming).
Lewis, D. (1973). Counterfactuals. Cambridge: Harvard University Press.
Nozick, R. (1981). Philosophical explanations. Cambridge: Harvard University Press.
Quine, W. V. O. (1981). Theories and things. Cambridge: Harvard University Press.
Acknowledgment
I would like to thank Michael Levin and two anonymous referees for their helpful comments on drafts of this paper.
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Alfano, M. Sensitivity Theory and the Individuation of Belief-Formation Methods. Erkenn 70, 271–281 (2009). https://doi.org/10.1007/s10670-008-9127-9
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DOI: https://doi.org/10.1007/s10670-008-9127-9