Forty-one years ago, in August 1963, I entered graduate school in the Department of Philosophy at the University of Pittsburgh. At that time, the “post-positivist” reaction to logical empiricism in philosophy of science was well under way, although not yet in full swing. In evolutionary biology, the “synthetic theory of evolution” seemed to have won a clear victory over its major rivals. In molecular biology, Watson and Crick's proposed structure for DNA, just a decade old, was widely accepted and was serving as a fulcrum for restructuring genetics as part of molecular biology, even though “the” genetic code had not yet been fully solved. (I use scare quotes because, within twenty years after the code was fully deciphered in 1966, it was discovered that some organisms have small systematic variations in the correlations between codons and amino acids. The code can vary even within a single organism: The mitochondria of many organisms employ slight variations on the standard code so that the nuclear and mitochondrial codes differ in specific ways.)

As a physics major and then a math major in college, I had taken no courses in biology. But, my father was a research ophthalmologist and, within two years of starting graduate studies, I realized that the sort of work he did (which I knew largely by osmosis) did not fit well with the dominant positions in philosophy of science.