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In the 1950's and 60's there arose a plethora of claims that the structure of evolutionary theory was intrinsically different from the structures of the theories of physics—and thus from the structure that philosophers of science claimed to be the structure of scientific theories. There were claims:1)that evolutionary theory had no laws (Smart 1963);2)that evolutionary concepts were so peculiar that their definitions violated the ordinary standards for definitions (Beckner 1959);3)that evolutionary theory was not axiomatizable (Beckner 1959);4)that evolutionary theory made no falsifiable predictions (Scriven 1959, Manser 1965, Smart 1963);5)that evolutionary biology relied on teleological explanations which violated the deductive-nomological explanation form (Hempel 1965); and6)that evolutionary biology made significant use of narrative explanations which also violated the deductive-nomological explanation form (Goudge 1961)

An apparently peculiar form of explanation is found in evolutionary biology (and other historical fields); it is called a genetic explanation by Beckner (1959) (and, in a more general discussion, by Hempel (1965)), a narrative explanation by Goudge (1961), and a Darwinian history by Kitcher (1985). Kitcher, assuming that the Darwinian history has some kind of logically respectable structure, is primarily concerned with arguing that it is the cornerstone of Darwin’s historical methodology; Beckner and Goudge, on the other hand, assuming that the genetic (or narrative) explanation is an important part of evolutionary biology, are primarily concerned with the difficulty of fitting this form of explanation into a logically respectable structure. Adopting the narrative explanation terminology, and assuming that the narrative explanation is central to Darwin’s historical methodology and to the methodology of contemporary evolutionary biology, I will in this paper delineate its logically respectable structure.

The philosophical literature is heavy with discussions of the logical structure of various proposed schema of functional explanation (most of which are modifications of Hempel's schema [7]) but it is very light on detailed analysis of the way in which these schema actually work or the way in which they apply to the instances in which functional explanations are used by scientists. These papers use statements by scientists ascribing particular functions to particular traits, along with intuitions about the way in which ‘function’ is used in ordinary language, to ascertain the referents of the term and thus to determine the class of uses against which any schema should be tested; but such examples only show whether the schema under discussion refer to the same things as those the scientists’ refer to; they do not show whether the logical structure of the schema really captures the logical structure underlying the scientists’ use.