It's widely supposed that unification is an epistemic virtue: the degree to which a theory is unified contributes to its overall confirmation. However, this supposition has consequences which haven't been noted, and which undermine the leading accounts of unification. For, given Hempel's equivalence condition, any epistemic virtue must be such that logically equivalent theories must equally well unify any body of evidence, and logically equivalent bodies of evidence must be equally well unified by any theory. Yet the leading accounts of (...) unification in Bayesian terms, or those in terms of argument patterns, cannot satisfy these constraints conditions. The reason for this runs deep: these accounts of unification make unity depend on factors that vary between equivalent theories: the probabilistic relations of their components, or their relations to argument patterns. The solution is to abandon such accounts and instead adopt an account of unity based on worldly relations such as causation, rather than inferential relations. Such an account effortlessly satisfies the equivalence conditions, and so may describe the epistemic virtue of unity. (shrink)

The adverse reaction to Hempel's 'ravens paradox' embodied in giving it that description is compared with the usual reaction of experimental subjects to the Wason selection task.

Several standard conditions of adequacy for confirmation are considered and a conclusion of B. Skyrms regarding the converse-consequence condition is shown to be mistaken. Widely accepted conditions such as the entailment condition and the special consequence condition are shown to be open to counterexample, and confusion about these conditions is traced to confusion about the difference between two kinds of confirmation concepts--concepts of firmness and concepts of increase in firmness. The importance of concepts of the latter sort is stressed. Finally, (...) some suggestions are offered relating to the notion of selective confirmation. (shrink)