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Many philosophers are again examining the traditional topic of a priori knowledge, or knowledge that does not depend on sensory experience. This volume collects the most important recent essays on the subject by well-known thinkers such as A.J. Ayer, W.V. Quine, Barry Stroud, C.I. Lewis, Hilary Putnam, Roderick M. Chisholm, Saul A. Kripke, Albert Casullo, R.G. Swinburne, and Philip Kitcher. Including an introduction by the editor and an extensive bibliography, this book provides philosophers and students with an in-depth look at contemporary investigations into the nature of a priori knowledge.

In his recent book Albert Casullo rejects the claim that if a belief is defeasible by non-experiential evidence then it is defeasible by experiential evidence. This claim is a crucial premise in a simple argument for the experiential defeasibility of a priori justification. I defend the premise against Casullo's objection, the main problem with which is that he does not take into account the evidential role of multiple corroborating sources of testimony. I conclude that the crucial premise is true and that the simple argument is sound; thus many of our a priori justified beliefs are experientially defeasible.

Tyler Burge offers a theory of testimony that allows for the possibility of both testimonial a priori warrant and testimonial a priori knowledge. I uncover a tension in his account of the relationship between the two, and locate its source in the analogy that Burge draws between testimonial warrant and preservative memory. I contend that this analogy should be rejected, and offer a revision of Burge's theory that eliminates the tension. I conclude by assessing the impact of the revised theory on the scope of a priori knowledge.

It seems to me that discussions of the past decades have made clear how intricate and complex the classical notion of the a priori is, and neither the Strong conception nor the Weak conception (nor anything else) can provide a coherent explication. (Kitcher 2000.

In a recent and interesting paper “Experientially Defeasible A Priori Justification,” Joshua Thurow argues that many a priori justified beliefs are defeasible by experience. The argument takes the form of an objection against Albert Casullo’s recent book, A Priori Justification, where Casullo, according to Thurow, denies that if a justified belief is non-experientially defeasible, then that belief is also experientially defeasible. This paper critically examines Thurow’s two arguments in the first two sections I–II. In the last section, III, an alternative line of argument for Thurow’s thesis is suggested that employs other parts of the framework that Casullo provides—especially the thesis of overdetermination of justification. It will be argued that the prospects for this suggestion are brighter than for bothof Thurow’s arguments.

John MacFarlane has recently presented a novel argument in support of truth- relativism. According to this, contextualists fail to accommodate retrospective reassessments of propositional contents, when it comes to languages which are rich enough to express actuality. The aim of this note is twofold. First, it is to argue that the argument can be effectively rejected, since it rests on an inadequate conception of actuality. Second, it is to offer a more plausible account of actuality in branching time, along the line of Lewis (1970/1983).

Some logical properties of modal languages in which actuality is expressible are investigated. It is argued that, if a sentence like 'Actually, Quine is a distinguished philosopher' is understood as a special case of world-indexed sentences (the index being the actual world), then actuality can be expressed only under strong modal assumptions. Some rival rigid and indexical approaches to actuality are discussed.

(K1) All knowledge of necessary propositions is a priori. (K2) All propositions known a priori are necessary. (K3) All knowledge of analytic propositions is a priori; and (K4) Some propositions known a priori are synthetic.

The major divide in contemporary epistemology is between those who embrace and those who reject a priori knowledge. Albert Casullo provides a systematic treatment of the primary epistemological issues associated with the controversy. By freeing the a priori from traditional assumptions about the nature of knowledge and justification, he offers a novel approach to resolving these issues which assigns a prominent role to empirical evidence. He concludes by arguing that traditional approaches to the a priori, which focus primarily on the concepts of necessity and analyticity, are misguided.