Information and Inaccuracy
William A. Roche, Tomoji Shogenji · The British Journal for the Philosophy of Science · 2016
This article proposes a new interpretation of mutual information (MI). We examine three extant interpretations of MI by reduction in doubt, by reduction in uncertainty, and by divergence. We argue that the first two are inconsistent with the epistemic value of information (EVI) assumed in many applications of MI: the greater is the amount of information we acquire, the better is our epistemic position, other things being equal. The third interpretation is consistent with EVI, but it is faced with the problem of measure sensitivity and fails to justify the use of MI in giving definitive answers to questions of information. We propose a fourth interpretation of MI by reduction in expected inaccuracy, where inaccuracy is measured by a strictly proper monotonic scoring rule. It is shown that the answers to questions of information given by MI are definitive whenever this interpretation is appropriate, and that it is appropriate in a wide range of applications with epistemic implications. 1 Introduction2 Formal Analyses of the Three Interpretations 2.1 Reduction in doubt 2.2 Reduction in uncertainty 2.3 Divergence3 Inconsistency with Epistemic Value of Information4 Problem of Measure Sensitivity5 Reduction in Expected Inaccuracy6 Resolution of the Problem of Measure Sensitivity 6.1 Alternative measures of inaccuracy 6.2 Resolution by strict propriety 6.3 Range of applications7 Global Scoring Rules8 Conclusion