Certainty: A Refutation of Scepticism by Peter Klein (review)

690 BOOK REVIEWS idea of a contingent connection between assertability and truth, and the idea of objectivism. These ideas, he argues, are "unnecessary and undefended ," ;and need not be included in a defense of realism. He concludes that Taylor's arguments "may reasonably persuade us to remain faithful to the literal interpretation of evaluations, and in that sense to profess evaluative relativism" (237). In an unfortunately brief application of this conclusion to the philosophy of the social sciences, Pettit reaffirms his support of Taylor's suggestion that evaluative realism makes possible "a dimension of critical interaction (in) cross-cultural interpretation " (241) . Readers interested in finding arguments in Wittgenstein's texts, and in bringing those arguments to bear on traditional philosophical topics, will find this volume both germane and challenging. Those who are convinced that Wittgenstein's work has radically reoriented the problems of philosophy will be impatient with these essays, while those who seek edification may find only an occasional glimmer. JOHN CHURCHILL Hendrix College Conway, .Arkansas Cei·tainty: A Refutation of Scepticism. By PETER KLEIN. Minneapolis: University of Minnesota Press, 1981. Pp. 230. 'l'his book consists of a single, rigorous argument against the most plausible forms of general scepticism. It argues against: Direct Scepticism (No person, S, can know that p, where "p " stands for any empirical , contingent proposition); Iterative Scepticism (S cannot know that S knows that p); and Pyrrhonian Direct Scepticism (There are no better reasons for believing S can know that p than there are for believing S cannot know that p). The sceptic argues that some condition necessary for knowledge cannot possibly be fulfilled for empirical propositions. Descartes's evil genius argument is the most famous example of this approach. Updated versions are the "Googal " and the "terrible Dr. 0 " hypotheses. For example , the latter is that Dr. O, an evil super-scientist, has invented a machine called a " braino." w·hen the " braino cap " is placed on the head of a subject, it affects his brain so as to produce whatever hallucinations the " braino's " operator desires, which may be as complete, systematic, and coherent as wished. The hypothesis is that I am actually plugged into the braino and experience nothing but its artificial stimuli. Such a hypothesis, the argument continues, is logically possible. But, BOOK REVIEWS 691 if a belief is completely justified, then those with which it conflicts are unjustified. Now, none of the evidence we possess for empirical proposi~ tions (perceptual evidence) makes the "Dr. 0" hypothesis (or the " Googal " or " Evil Genius " hypotheses) logically impossible. Therefore , the sceptic concludes, our beliefs in empirical propositions cannot be justified. Klein shows that the argument implicitly supposes the following basic epistemic maxim : " In order to be justified in believing that p, S must be justified in rejecting either the contrary of p, or what would defeat the evidence for p." This epistemic maxim may be understood in various ways. First, the supposition may be that " a prerequisite of S's being justified in believing that p, is that S be justified in denying the contrary of p." In this case, before I can know there are rocks (say), I must be justified in rejecting the contrary of this belief, e.g., that an evil scientist is causing me falsely to believe there are rocks. Klein calls this the " Contrary Prerequisite Elimination Principle." Klein has little trouble showing this principle to be invalid. The detective , for example, scarcely need disprove every logically possible candidate before he proves that so-and-so was the murderer-excluding key suspects, or even sometimes directly proving the murderer's identity, will suffice. A second interpretation of the sceptic's argument would be: Before S is justified in believing that p, S must be justified in denying all the defeaters of the evidence S has for p. By " defeater" is meant a proposition which, when joined to the evidence for p, neutralizes its evidential value. This principle, however, entails the Contrary Prerequisite Principle (refuted above), and so by modus tollens is also refuted. (Klein also considers modified versions of the Contrary Prerequisite Principle (104-109), but finds them defective or not supportive of the sceptic's conclusion .) The...