Deduction leads to causal explanation in phylogenetic inference when the evidence, the systematic character, is conceptualized as a transformation series. Also, the deductive entailment of modus tollens is satisfied when those kinds of events are operationalized as patristic difference. Arguments to the contrary are based largely on the premise that character-states are defined intensionally as objects, in terms of similarity relations. However, such relations leave biologists without epistemological access to the causal explanation and explanatory power of historical statements. Moreover, the (...) prediction-making to which those kinds of relations are limited in practice can lead to a category error—the mental conversion of an abstraction into a thing . The latter practices and problems characterize pattern cladistics, taxa being interpreted as homeostatic property cluster natural kinds, and other instrumentalist research programs. (shrink)