Dretske on reasons and justification

Abstract

For any proposition P, if S is justified in believing P, and P entails Q, and S deduces Q from P and accepts Q as a result of this deduction, then S is justified in believing Q. While this principle seems unexceptionable Dretske has a counterexample which convinces him that the principle must be rejected. I shall argue that the principle is perfectly sound if certain general cautions, applicable to any argument, are observed. These cautions will, I believe, dispose of Dretske's counter-example. The counter-example may be briefly stated as follows: An eight year old boy is told by a generally unreliable adult that a certain object is a yardstick. The boy then sees his father pick up the yardstick and put it in the closet. Dretske now (op. cit., p. 167) puts his objection. 'But is the child justified in believing that it was a yardstick that his fatherfut in the closet? P (His father put the yardstick in the closet) does entail Q (It was a yardstick that his father put in the closet), but I do not think the child is justified in believing Q simply because he is justified in believing P and realizes that P entails Q' (emphasis Dretske's). The point is, of course, that the object may or may not have been a yardstick. My general criticism is that Dretske is playing upon the possibility of referential opacity in descriptions of actions. Verbs of action are always (I think) capable of taking as their objects either what the object is when truly described or what the object is under a description the agent thinks to be true. It is the former case we have in mind when we say without qualms that Columbus discovered America. But if we happen to be thinking about what Columbus thotught he discovered, and about the fact that 'America' is named after Amerigo Vispucci who had not even been there (where?) when Columbus arrived, then we may begin to have qualms--and the latter interpretation of action verbs becomes relevant. Certainly a basic, though surely not infallible, way of finding out what a person is doing is to ask him; and if someone had asked Columbus at the time what he was doing he would not, and could not, have said that he was discovering America. Now I don't think these two possible interpretations of sentences with action verbs need give us any real philosophical trouble, although I 1 'Reasons and Consequences', ANALYSIS, 28. 5. 100