Darwin’s Pangenesis and the Problem of Unconceived Alternatives1

In earlier work I have argued that the most substantial threat to scientific realism arises from the problem of unconceived alternatives: the repeated failure of past scientists and scientific communities to conceive of alternatives to extant scientific theories, even when such alternatives were both (1) well confirmed by the evidence available at the time and (2) sufficiently scientifically serious as to be later embraced by actual scientific communities. In this paper I explore Charles Darwin’s development and defense of his ‘pangenesis’ theory of inheritance and conclude that this particular historical example offers impressive support for the challenge posed to realism by this problem of unconceived alternatives.