Philosophy in Review XXX (2010), no. 3 186 Michael Forster Kant and Skepticism. Princeton: Princeton University Press 2008. 166 pages US$32.95 (cloth ISBN 978-0-691-12987-7) US$19.95 (paper ISBN 978-0691146515) The central contention of this book is that Kant, in the formulation and development of his critical philosophy, was primarily motivated by two kinds of skepticism, neither of which was the skepticism about the existence of a mind-independent external world as formulated by Descartes ('veil of perception' skepticism). Forster focuses instead on Humean skepticism (regarding the possibility of a priori concepts and synthetic a priori knowledge) and Pyrrhonian skepticism (the practice of inducing suspension of judgment through the opposition of rival arguments which seem equipollent). The author thereby places himself in opposition to the orthodox interpretation, which is that external world skepticism is key to understanding the motivation and development of Kant's philosophy. (For a recent exposition in agreement with the orthodox interpretation, see Luigi Caranti, Kant and the Scandal of Philosophy: The Kantian Critique of Cartesian Scepticism. UTP, 2007.) More precisely, Forster contends that the two main concerns addressed by the critical philosophy-namely, to respond to skepticism and to develop a reformed metaphysics-are intimately related because Kant was mainly concerned with those forms of skepticism primarily directed at metaphysics. Although metaphysical claims are among the targets of external world skepticism, only in the Humean and the Pyrrhonian varieties are they the main targets. Forster's claim that Cartesian skepticism was a secondary concern for Kant is but one of the two unorthodox aspects of his interpretation. Given that the significance of Hume's skepticism in Kant's thought is in fact widely recognized, the second 'heretical' aspect is the claim that Kant underwent a crise pyrrhonienne. Surprising in this regard is the lack of any mention of Richard Popkin's well-known thesis that modern philosophy in general developed out of a Pyrrhonian crisis, triggered especially by the Renaissance rediscovery of Sextus Empiricus' extant writings. The book is divided into two parts, the first expounding Forster's interpretation of Kant's stance on the different varieties of skepticism, and the second critically evaluating the efficacy of the latter's anti-skeptical strategies. Forster's arguments, which presuppose that the reader is well acquainted with the main elements of Kant's critical philosophy, are in general convincing. The rival interpretations typically targeted are those in the Anglophone tradition. The first part's lead chapter presents the aforementioned distinction between three forms of skepticism and the thesis that Kant was mainly concerned with the Humean and Pyrrhonian skeptical positions. The second chapter purports to show that Philosophy in Review XXX (2010), no. 3 187 veil of perception skepticism played no significant part in either the origination or the mature motivation of the critical philosophy. In the writings from the pre-critical period, discussion of this type of skepticism is rare and brief. As for the critical period, Kant responds to it only in the Fourth Paralogism of the first edition of the Critique and in the Refutation of Idealism of the second edition. Forster argues that the pre-critical and critical texts addressing external world skepticism are primarily concerned with metaphysical issues having nothing to do with this skeptical position, and that its refutation is a by-product of the stance Kant came to adopt in discussing those issues. Although I find Forster's general interpretation persuasive, Kant's claim, in the second edition of the Critique, that it was a 'scandal' that philosophy had been unable to provide an irrefutable proof of the existence of the external world, poses a serious problem for that interpretation. And I do not think that the claim in question can easily be accounted for by saying that 'the new prominence of "veil of perception" skepticism' is to be ascribed to 'an author's natural tendency to emphasize his latest material' (11). The third chapter explains away an apparent inconsistency in Kant's explanation of what aroused him from his 'slumber' of dogmatic metaphysics and drove him towards the critical philosophy. At one time, he claimed that the motivation was Hume's attack on causal reasoning but, at another, that it was the antinomies of pure reason. Forster claims that Kant was referring to the two forms of skepticism (Humean and Pyrrhonian) which he encountered at different moments of his life. The next two chapters address the impact of both Pyrrhonism and Humean skepticism on Kant. In Chapter 4, Forster deals with the Pyrrhonian crisis that Kant underwent in the mid-1760s, which made him realize that there were conflicting but equally persuasive metaphysical claims and that this situation of equipollence led to suspension of judgment. The impact of Humean skepticism is examined in Chapter 5. Whereas in Pyrrhonism Kant found a serious challenge to the dogmatic metaphysics he adopted before the mid-1760s, in Humean skepticism he found a serious challenge to the momentary metaphysical relapse he suffered in his Inaugural Dissertation of 1770, in which he held that the intellect can acquire knowledge of supersensible noumena. Hume's attack on causation reinforced Kant's worries about the existence and reference of a priori concepts and the possibility of synthetic a priori knowledge. The sixth chapter maintains that the main features of Kant's reformed metaphysics-namely, its concern with objects of possible experience, its focus on the world as constituted by our own minds, and its systematicity-were introduced in order to meet the challenges posed by Pyrrhonism and Humean skepticism. The two remaining chapters of the first part analyze how those features work against these two varieties of skepticism. Against Humean skepticism, Kant invokes transcendental arguments to prove that specific metaphysical a priori concepts refer and that specific metaphysical synthetic a priori principles are true; such arguments establish that the reference of those concepts or the truth of those principles is a condition of the possibility of experience. Transcendental idealism is part of the response to Pyrrhonism, since it shows that the Philosophy in Review XXX (2010), no. 3 188 conflicts involved in the antinomies are actually illusory. In addition, Kant thinks the Pyrrhonist would accept his proofs that specific metaphysical concepts and principles refer and are true, respectively. This is so because the Pyrrhonist (as Kant conceives him) calls into question neither experiential judgments nor logical principles. Finally, given Kant's assumption that metaphysics is a science and his demonstration (which the Pyrrhonist would be forced to accept) that the metaphysical concepts and principles he has vindicated constitute an entire system, all the remaining problematic principles must be expelled from the domain of metaphysics. Although Forster's knowledge of ancient Pyrrhonism is in general fairly good, he makes the surprising claim that for Pyrrhonism, as at one point for Kant, the concepts of 'the useful, happiness, and everyday life ... functioned as a prominent normative ideal' (19). This is surprising because the Pyrrhonist would consider normative ideals to be highly dogmatic, i.e., as based on assertions about how things really are. Chapter 9 (the first chapter of the second part) addresses two apparent problems for Kant's use of the term 'metaphysics' and his project of defending metaphysics, problems which Forster thinks can be easily solved. The next two chapters deal with more serious difficulties. Chapter 10 is mainly concerned with an inconsistency in Kant's position on the metaphysics of morals in the Critique: the claim that morality is a matter of sentiments runs counter to the official cognitivist theory of morality of the critical period. For its part, Chapter 11 criticizes Kant's 'failure of self-reflection', i.e., a failure to realize that the claims made in order to solve the difficulties faced by other claims actually confront very similar difficulties. For instance, the claims about transcendental idealism are neither analytic nor known from experience, so they must be synthetic a priori. But given that no synthetic a priori claim in metaphysics should be accepted unless one can explain how it can be known, and given that the only such explanation is transcendental idealism's thesis of mind-imposition, one is led to the conclusion that the synthetic a priori thesis of transcendental idealism is known because it is mind-imposed. Since this is absurd, Kant should have followed his own principles and refrained from asserting that metaphysical thesis. The final chapter argues that Kant considered his response to the Pyrrhonian challenge to be successful only because he interpreted Pyrrhonism as a moderate form of skepticism which does not target empirical, mathematical, or logical claims, but restricts its attack to those of supersensible metaphysics. But if Pyrrhonism is interpreted-as Forster in agreement with Hegel interprets it-as a radical form of skepticism which also targets those various types of claims, then such a response fails. I highly recommend this book to those working on Kant's philosophy, the general history of modern skepticism, or the influence of Pyrrhonism on modern thought. Diego E. Machuca Consejo Nacional de Investigaciones Científicas y Técnicas (Argentina)