HOW TO TELL WHEN SIMPLER, MORE UNIFIED, OR LESS AD-HOC THEORIES WILL PROVIDE MORE ACCURATE PREDICTIONS

Traditional analyses of the curve fitting problem maintain that the data do not indicate what form the fitted curve should take. Rather, this issue is said to be settled by prior probabilities, by simplicity, or by a bacgkround theory. In this paper, we describe a result due to Akaike [1973], which shows how the data can underwrite an inference concerning the curve's form based on an estimate of how predictively accurate it will be. We argue that this approach throws light on the theoretical virtues of parsimoniousness, unification. and non ad hocness, on the dispute about Bayesianism, and on empiricism and scientific realism.