Consilience and Natural Kind Reasoning

Abstract

In his ongoing debate with Clark Glymour and other scientific realists, Bas van Fraassen (e.g. 1983 pp. 165–168, 1985 p. 247 pp. 280–281 pp. 294–295) has often appealed to a widely accepted doctrine that strength and security are conflicting virtues which must be traded off one against the other. In limiting his commitment to only the empirical adequacy of a theory van Fraassen claims to be simply more cautious than his realist opponents. Certainly, as he delights in pointing out, a theory T cannot be more probable than its empirical consequences E. For Probability is monotone with respect to entailment, so P(T) ≤ P(E) if T entails E. If security is measured by any function which, like probability, is monotone with entailment, then it would seem that the kind of trade-off between strength and security van Fraassen appeals to is unavoidable.1