Evidence and Leverage: Comment on Roush
Author: Barnes, Eric Christian
Source: British Journal for the Philosophy of Science, Volume 59, Number 3, 7 September 2008 , pp. 549-557(9)
Publisher: Oxford University Press
Abstract:Sherrilyn Roush's Tracking Truth provides a sustained and ambitious development of the basic idea that knowledge is true belief that tracks the truth. In this essay, I provide a quick synopsis of Roush's book and offer a substantive discussion of her analysis of scientific evidence. Roush argues that, for e to serve as evidence for h, it should be easier to determine the truth value of e than it is to determine the truth value of h, an ideal she refers to as leverage. She defends a detailed method by which the value of p(he) is computed without direct information about p(h) but only using evidence about the value of p(e), from which the value of p(h) is derived. She presents an example of how to use her leverage method, which I argue involves a certain critical mistake. I show how the leveraging method can be used in a way that is soundI conclude with a few remarks about the importance of distinguishing clearly between prior and posterior probabilities.
Document Type: Review article
Publication date: 2008-09-07
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