The logical interpretation of probability, or "objective Bayesianism'' – the theory that (some) probabilities are strictly logical degrees of partial implication – is defended. The main argument against it is that it requires the assignment of prior probabilities, and that any attempt to determine them by symmetry via a "principle of insufficient reason" inevitably leads to paradox. Three replies are advanced: that priors are imprecise or of little weight, so that disagreement about them does not matter, within limits; that it (...) is possible to distinguish reasonable from unreasonable priors on logical grounds; and that in real cases disagreement about priors can usually be explained by differences in the background information. It is argued also that proponents of alternative conceptions of probability, such as frequentists, Bayesians and Popperians, are unable to avoid committing themselves to the basic principles of logical probability. (shrink)

Peter Achinstein has argued at length and on many occasions that the view according to which evidential support is defined in terms of probability-raising faces serious counterexamples and, hence, should be abandoned. Proponents of the positive probabilistic relevance view have remained unconvinced. The debate seems to be in a deadlock. This paper is an attempt to move the debate forward and revisit some of the central claims within this debate. My conclusion here will be that while Achinstein may be right (...) that his counterexamples undermine probabilistic relevance views of what it is for e to be evidence that h, there is still room for a defence of a related probabilistic view about an increase in being supported, according to which, if p > p, then h is more supported given e than it is without e. My argument relies crucially on an insight from recent work on the linguistics of gradable adjectives. (shrink)

Perhaps personality traits substantially influence one’s philosophically relevant intuitions. This suggestion is not only possible, it is consistent with a growing body of empirical research: Personality traits have been shown to be systematically related to diverse intuitions concerning some fundamental philosophical debates. We argue that this fact, in conjunction with the plausible principle that almost all adequate philosophical views should take into account all available and relevant evidence, calls into question some prominent approaches to traditional philosophical projects. To this end, (...) we present the Philosophical Personality Argument (PPA). We explain how it supports the growing body of evidence challenging some of the uses of intuitions in philosophy, and we defend it from some criticisms of empirically based worries about intuitions in philosophy. We conclude that the current evidence indicates that the PPA is sound, and thus many traditional philosophical projects that use intuitions must become substantially more empirically oriented. (shrink)

Jean Perrin’s argument for the existence of molecules from his 1908 experimental determination of Avogadro’s number raises two questions considered in this article. One is historical: Why as late as 1908 should Perrin have thought it necessary to argue that molecules exist? The other, which takes up the bulk of this article, is philosophical: In view of the fact that his argument appears to assume the existence of molecules as a premise, how, if at all, can a charge of circularity (...) be avoided? I criticize attempted reconstructions of his argument by Salmon, Glymour, and hypothetico-deductivists. And I propose a probabilistic solution that avoids circularity. Finally, I consider whether Perrin’s reasoning, so construed, is an empirical argument for scientific realism. (shrink)