What is required for something to be evidence for a hypothesis? In this fascinating, elegantly written work, distinguished philosopher of science Peter Achinstein explores this question, rejecting typical philosophical and statistical theories of evidence. He claims these theories are much too weak to give scientists what they want--a good reason to believe--and, in some cases, they furnish concepts that mistakenly make all evidential claims a priori. Achinstein introduces four concepts of evidence, defines three of them by reference to "potential" evidence, (...) and characterizes the latter using a novel epistemic interpretation of probability. The resulting theory is then applied to philosophical and historical issues. Solutions are provided to the "grue," "ravens," "lottery," and "old-evidence" paradoxes, and to a series of questions. These include whether explanations or predictions furnish more evidential weight, whether individual hypotheses or entire theoretical systems can receive evidential support, what counts as a scientific discovery, and what sort of evidence is required for it. The historical questions include whether Jean Perrin had non-circular evidence for the existence of molecules, what type of evidence J. J. Thomson offered for the existence of the electron, and whether, as is usually supposed, he really discovered the electron. Achinstein proposes answers in terms of the concepts of evidence introduced. As the premier book in the fabulous new series Oxford Studies in Philosophy of Science, this volume is essential for philosophers of science and historians of science, as well as for statisticians, scientists with philosophical interests, and anyone curious about scientific reasoning. (shrink)

Consider the skeptic about the external world. Let’s straightaway concede to such a skeptic that perception gives us no conclusive or certain knowledge about our surroundings. Our perceptual justification for beliefs about our surroundings is always defeasible—there are always possible improvements in our epistemic state which would no longer support those beliefs. Let’s also concede to the skeptic that it’s metaphysically possible for us to have all the experiences we’re now having while all those experiences are false. Some philosophers dispute (...) this, but I do not. The skeptic I want to consider goes beyond these familiar points to the much more radical conclusion that our perceptual experiences can’t give us any knowledge or even justification for believing that our surroundings are one way rather than another. (shrink)

Something about this argument sounds funny. As we’ll see, though, it takes some care to identify exactly what Moore has done wrong. Iwill assume that Moore knows premise (2) to be true. One could inquire into how he knows it, and whether that knowledge can be defeated; but Iwon’t. I’ll focus instead on what epistemic relations Moore has to premise (1) and to his conclusion (3). It may matter which epistemic relations we choose to consider. Some philosophers will diagnose Moore’s (...) argument using Contextualist machinery. They’ll say. (shrink)

What is the epistemological value of perceptual experience? In his recently influential paper, “The Skeptic and the Dogmatist”1, James Pryor develops a seemingly plausible answer to this question. Pryor’s answer comprises the following three theses: (F) “Our perceptual justification for beliefs about our surroundings is always defeasible – there are always possible improvements in our epistemic state which would no longer support those beliefs.” (517) (PK) “This justification that you get merely by having an experience as of p can sometimes (...) suffice to give you knowledge that p is the case.” (520) (D) “When it perceptually seems to you as if p is the case, you have a kind of justification for believing p that does not presuppose or rest on your justification for anything else, which could be cited in argument (even an ampliative argument) for p. To have this justification for believing p, you need only have an experience that represents p as being the case. No further awareness or reflection or background beliefs are required.” (519) Let’s use the phrase “fallibilist dogmatism” to refer to the conjunction of (F), (PK), and (D).2 Pryor does not argue for either (F) or (PK) in his paper; he simply shares the widespread and plausible assumption that (F) and (PK) are both true. But the conjunction of (F) and (PK) implies that we can have knowledge on the basis of defeasible justification. And this view leads to paradox. Consider the following individually plausible but jointly incompatible statements. (shrink)

I argue that its appearing to you that P does not provide justification for believing that P unless you have independent justification for the denial of skeptical alternatives – hypotheses incompatible with P but such that if they were true, it would still appear to you that P. Thus I challenge the popular view of ‘dogmatism,’ according to which for some contents P, you need only lack reason to suspect that skeptical alternatives are true, in order for an experience as (...) of P to justify belief that P. I pursue three lines of objection to dogmatism, having to do with probabilistic reasoning, considerations of future or hypothetically available justification, and epistemic circularity. I briefly sketch a fall-back position which avoids the problems raised. (shrink)

The Realm of Reason develops a new, general theory of what it is for a thinker to be entitled to form a given belief. The theory locates entitlement in the nexus of relations between truth, content, and understanding. Peacocke formulates three principles of rationalism that articulate this conception. The principles imply that all entitlement has a component that is justificationally independent of experience. The resulting position is thus a form of rationalism, generalized to all kinds of content. To show how (...) these principles are realized in specific domains, Peacocke applies the theory in detail to several classical problems of philosophy, including the nature of perceptual entitlement, induction, and the status of moral thought. These discussions involve an elaboration of the structure of entitlement in ways that have applications in many other areas of philosophy. He also relates the theory to classical and recent rationalist thought, and to current issues in the theory of meaning, reference and explanation. In the course of these discussions, he proposes a general theory of the a priori. The focus of the work lies in the intersection of epistemology, metaphysics, and the theory of meaning, and will be of interest both to students and researchers in these areas, and to anyone concerned with the idea of rationality. (shrink)

He then argues that (1), (2) and (3) constitute an inconsistent triad as follows (1991, p. 15): Suppose (1) that Oscar knows a priori that he is thinking that water is wet. Then by (2), Oscar can simply deduce E, using premisses that are knowable a priori, including the premiss that he is thinking that water is wet. Since Oscar can deduce E from premisses that are knowable a priori, Oscar can know E itself a priori. But this contradicts (3), (...) the assumption that E cannot be known a priori. Hence (1), (2), and (3) are inconsistent. McKinsey’s conclusion is that ‘anti-individualism is inconsistent with privileged access’ (ibid.). (shrink)