Abstract

The knowledge norm of assertion is mainly in competition with a high probability or rational credibility norm. The argument for the knowledge norm that I offer turns on cases in which a hearer responds to a speaker's assertion by asserting another sentence that would lower the probability of the speaker's assertion, were its probability less than one. In cases like this, though with qualifications, is the hearer's contribution a challenge to the speaker's assertion or complementary to it? My answer is the latter, and that only the knowledge norm yields that answer.The cases that I rely on follow from an elementary probability relation, though one that is inconsistent with the still influential relevance criterion for confirmation and evidence . Assume, for illustrative purposes, that p is in your belief corpus, as a consequence of your believing ∨ ∨ . 1 You learn that ∼ & ∼ , which would lessen the probability of p, were its probability less than one, 2 since it eliminates two rows of the truth-table in which p holds. What conclusion do you reach about p?Rather than withdrawing p, you acquire the belief that p & ∼ s & ∼ r, even though Formula where pr would be the subjective or epistemic probability of p on a probabilistic view of the knowledge norm before learning ∼ & ∼ . Instead of withdrawal …