Abstract

Confirmation theorists have frequently expressed an interest in evidence which strengthens a hypothesis or in evidence which makes a hypothesis firmer. A number of criteria have been offered, including the instantial criterion, the prediction criteria, and Hempel's satisfaction criterion. All of these criteria are dyadic, but the concept of strengthening evidence is triadic, for it makes explicit reference to an evidence report and a hypothesis, and implicit reference to prior evidence in the light of which a new evidence report must be evaluated. I argue that the approach to strengthening evidence reflected in these criteria is inadequate, that is, that dydic criteria can be of only limited value in connection with a triadic concept. I discuss the possibility that these criteria have been offered for the concept of initially strengthening evidence. The latter explanation is rejected, and other explanations for having failed to consider prior evidence are discussed.