A note on defeasibility and skepticism

Abstract

In response to the Gettier counter-examples, some philosophers have sought to add a condition to the traditional analysis of knowledge as justified true belief. Let us refer to any such fourth condition which requires that the agent stand in some epistemic relation to the problematic "essential" steps in the Gettier cases, as an epistemic fourth condition, and any fourth condition which requires simply that the step(s) possess a given property (generally, truth), independently of anyone's knowledge of it, as a metaphysical fourth condition. Thus a rough characterization of the fourth condition imposed by defeasibility analysts holds that X knows that p only if (iv) there is no true statement q, such that when q is added to the justification that p, the justification is defeated. We are mainly concerned here with arguing against any such metaphysical fourth condition because it leads to an unacceptable kepticism. It is not surprising that no one has seriously proposed an epistemic fourth condition. The Gettier case turns on the possibility that even with the best justification for a statement, it can still be false. Any fallibilist, who does not take logical certainty as requisite for justification in knowledge, will face Gettier problems no matter how strong the epistemic conditions he imposes. Nonetheless, we should note that an epistemic fourth condition can be combined with a denial of the importance of the Gettier problem over the range of cases where ideal justification and truth diverge. On one hand, if we accept p, where p is the conclusion inferred from q which is itself supported by evidence e, then one is accepting something that is true. If we want to draw other inferences from q, and e does not cover all possible tests, then we will naturally be accepting q only provisionally. We will continue to subject it (q) to further tests, wherein, presumably, we will discover its falsity. On the other hand, if no further tests are relevant to determining the truth of q, it is not easy to see what difference it makes that we accept it. We are quite used to our knowledge improving while