On Higher-Order and Free-Floating Chances

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    Anglais

    Marc Lange ([2006]) considers what I call free-floating chances—objective chances that obtain at a given time despite the fact that their values are not determined by the laws of nature together with the full history of non-chancy facts up to that time. I offer an intuitive example of this phenomenon, and use it to argue that free-floating chances are indeed possible. Their possibility violates three quite widely held principles about chances: the lawful magnitude principle, the principle that chances evolve by conditionalization and a version of David Lewis' principal principle. I argue that we should reject common formulations of each of these principles, though I offer revised understandings of each which retain much of the intuitive attractiveness of the originals and are consistent with the possibility of free-floating chances. I conclude by arguing that, while considerations of free-floating chances are important, they will not sustain the extravagant conclusions Lange attempts to draw from them. 1. Introduction 2. First- and Higher-Order Chances 3. Free-Floating Chances 4. Support for the Intuitive Assessment 5. Three Principles Violated 6. What to do? 7. COND as a Default Hypothesis 8. A More Principled Principal Principle 9. Conclusion

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