The main argument of this paper is that an evaluation of the overall explanatory power of a theory is less problematic and more relevant as an assessment of the state of knowledge than evaluation of statistical explanations of single occurrences in terms of likelihoods that are assigned to explananda.

The following values have no corresponding Zotero field: PB - Erlbaum Hillsdale, NJ.

An empirical law or evidence which supports a theory tends to have the greatest scientific value when it seemed improbable before it was investigated. Evidence which falsifies a theory tends to have the greatest value when it seemed probable that the investigation would confirm the theory. A scientist who wishes to optimize his contribution to knowledge probably will investigate most frequently hypotheses which seem neither very probable nor very improbable of being confirmed. This strategy leads neither to a maximum number (...) of confirmations of a theory, nor to a set of tests which are maximally severe. (shrink)

A theoretical framework Is presented that distinguishes among three knowledge sources that form the basis for generative performance. The three knowledge sources, termed conceptual, procedural, and utilizational competence, were implemented as a computational model that derives plans for counting procedures. In a previous analysis, Greeno, Riley, and Gelman (1984) developed a characterization of the conceptual competence (implicit understanding of general concepts and principles) associated with the skill of counting and related conceptual competence to various models of performance. In the current (...) work all three knowledge sources are formalized in a computer program (COUNTPLAN) that generates planning nets of counting procedures. The sufficiency of COUNTPLAN's knowledge components is demonstrated through its capacity to generate new plans for counting in novel settings from a core of conceptual competence. The utility of COUNTPLAN to facilitate the distinction between hypotheses of competence and hypotheses of performance is discussed. (shrink)