Abstract
In his earlier writings, Fred Dretske proposed an anti-skeptical strategy that is based on a rejection of the view that knowledge is closed under known entailment. This strategy is seemingly congenial with a sensitivity condition for knowledge, which is often associated with Dretske’s epistemology. However, it is not obvious how Dretske’s early account meshes with the information-theoretic view developed in Knowledge and the Flow of Information. One aim of this paper is to elucidate the connections between these accounts. First I argue that, contrary to an objection raised by Christoph Jäger, the information-theoretic account is compatible with Dretske’s anti-skeptical strategy based on the rejection of closure. This strategy invokes the notion of channel conditions, which are roughly speaking those conditions that are necessary and jointly sufficient for a signal to carry information. I propose an interpretation of the account that is based on the idea that a signal’s carrying information requires that the channel conditions are stable. It is shown that the resulting account incorporates both a sensitivity condition and a safety condition for knowledge. Finally, I demonstrate how this proposal allows for knowledge of modally robust propositions without making its acquisition too easy, as simple safety accounts do. I end with a suggestion concerning the direction that future research should take, based on the fact that in its present form the information-theoretic account does not capture inferential knowledge.
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Notes
In Dretske’s original formulation, the belief is of the form ‘s is F’. This way of putting things is motivated by his belief that mental contents are fundamentally de re (Dretske 1981, p. 68). Since I do not think that this commitment is necessary, I stick with the more neutral formulation throughout the paper.
As Barry Loewer notes in his discussion of Dretske’s definition, conditions in conditional probabilities have to be expressed by statements (Loewer 1982, p. 298). In the following, ‘r’ therefore stands for the fact that a certain signal obtains.
Since it may strictly speaking be incorrect to do so, I should add that the probabilistic version of the account is in principle dispensable. For another modal formulation of Dretske’s account, see D’Alfonso (2014).
For more on relevant alternatives, see Dretske (1971).
This may not be the most precise formulation of knowledge closure, but it suffices for my purposes. For a more sophisticated account, see, e.g., Hawthorne (2005).
Luciano Floridi (2014) endorses a variation of this thesis. Notice, however, that he—correctly—takes Dretske to reject it.
Note that it is at least not obvious that one can show that closure is violated in Dretske’s account, for the following reason. A counterexample to closure would have to involve a case in which a person knows a proposition P and knows that P entails another proposition Q. However, given that entailment involves necessitation, Dretske’s account, which is supposed to apply primarily to perceptual knowledge, does not allow for ‘P entails Q’ to be known.
In my view, the same applies to the position Dretske defended in Conclusive Reasons (Dretske 1971), which seems completely compatible with his information-theoretic account.
On an alternative formulation of basis safety, the basis must not obtain in any nearby worlds in which the belief is held but is not true. I will ignore the subtle differences between these versions here.
In the version of the information-theoretic account just developed, this can be explained by the fact that her reason is not sensitive, for the next possible world in which she faces a cleverly disguised mule is one in which her perceptual experience is the same.
This illustrates that the modified account I am proposing still involves sensitivity.
As an anonymous reviewer pointed out, this is not all that surprising, given the counterfactual clause involved in my account of information. For, the truth-value of counterfactual conditionals is not preserved when one strengthens the antecedent from P to (P & Q) or from (P v Q) to Q. Notice also that the purely counterfactual notion of information proposed by Cohen and Meskin (2006) is not closed under disjunction introduction or conjunction elimination, either—the latter is pointed out by Demir (2012).
On Dretske’s account, they are even a subset of the set of nomic possibilities.
Alternatively, one could require that for a signal to carry the information that a conjunction obtains, it needs to carry information about each conjunct. I do not wish to settle the question which of these options is to be preferred here.
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Acknowledgments
I have presented versions of this paper in Bonn and at MIT, and I am grateful to the audiences on those occasions for helpful comments. I am especially grateful for comments and discussions to Alma Barner, Nilanjan Das, Thomas Grundmann, Joachim Horvath, Christoph Jäger, Leon Leontyev, Marius Thomann, Stephen Yablo, and two anonymous referees of this journal.
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Kipper, J. Safety, Closure, and the Flow of Information. Erkenn 81, 1109–1126 (2016). https://doi.org/10.1007/s10670-015-9787-1
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DOI: https://doi.org/10.1007/s10670-015-9787-1