A SEMANTIC APPROACH TO COMPARATIVE VERISIMILITUDE

The importance of the comparative notion of verisimilitude, or truthli keness, for a realist conception of knowledge follows from two modest 'realist' assumptions, namely, that the aim of an enquiry, as an enqui ry, is the truth of some matter; and that one false theory may realize this aim better than another. However, there seem to be two ways in w hich one (false) theory can realize this aim better than another. One (false) theory can be closer to the truth than another either by being preponderantly more accurate in its predictions or by providing more comprehensive information about the system (or class of systems) at is sue. This paper presents a model-theoretic approach to the analysis of the comprehensiveness-related component of the comparative notion of verisimilitude. The machinery of the 'semantic' view of theories is ap plied to the problem of providing necessary and sufficient conditions for the truth of sentences of the form, 'B is truth-increasing with re spect to A', where A and B are taken to be sets of structures.