Ockham's Razor, Truth, and Information Kevin T. Kelly Department of Philosophy Carnegie Mellon University
[email protected] March 11, 2008 Abstract In science, one faces the problem of selecting the true theory from a range of al- ternative theories. The typical response is to select the simplest theory compatible with available evidence, on the authority of \Ockham's Razor". But how can a ¯xed bias toward simplicity help one ¯nd possibly complex truths? A short survey of standard answers to this question reveals them to be either wishful, circular, or irrelevant. A new explanation is presented, based on minimizing the reversals of opinion prior to convergence to the truth. According to this alternative approach, Ockham's razor does not inform one which theory is true but is, nonetheless, the uniquely most e±cient strategy for arriving at the true theory, where e±ciency is a matter of minimizing reversals of opinion prior to ¯nding the true theory. 1 Introduction Suppose that several or even in¯nitely many theories are compatible with the infor- mation available. How ought one to choose among them, if at all? The traditional and intuitive answer is to choose the \simplest" and to cite Ockham's razor by way of justi¯cation. Simplicity, in turn, has something to do with minimization of entities, de- scription length, causes, free parameters, independent principlies, or ad hoc hypotheses, or maximization of unity, uniformity, symmetry, testability, or explanatory power. Insofar as Ockham's razor is widely regarded as a rule of scienti¯c inference, it should help one to select the true theory from among the alternatives.