title: August Weismann's theory of the germ-plasm and the problem of unconceived alternatives.
abstract: I have argued elsewhere that scientific realism is most significantly challenged neither by traditional arguments from underdetermination of theories by the evidence, nor by the traditional pessimistic induction, but by a rather different historical pattern: our repeated failure to conceive of alternatives to extant scientific theories, even when those 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. Here I use August Weismann's defense of his influential germ-plasm theory of inheritance to support my claim that this pattern characterizes the history of theoretical scientific investigation generally. Weismann believed that the germ-plasm must become disintegrated into its constituent elements over the course of development, I argue, only because he failed to conceive of any possible alternative mechanism of ontogenetic differentiation. This and other features of the germ-plasm theory, I suggest, reflect a still more fundamental failure to imagine that the germ-plasm might be a productive rather than expendable resource for the cell. Weismann's case provides impressive support for the problem of unconceived alternatives while rendering its challenge to scientific realism deeper and sharper in a number of important ways.
authors.affiliation: Department of Logic and Philosophy of Science, University of California, Irvine, 5100 Social Science Plaza Irvine, CA 92697-5100, USA.
authors.forename: P Kyle
authors.initials: PK
authors.lastname: Stanford
mesh_terms: D005075:Biological Evolution; D002454:Cell Differentiation / Q000235:genetics; D005111:Extrachromosomal Inheritance / Q000235:genetics*; D014644:Genetic Variation / Q000235:genetics*; D005854:Germ Cells; D049672:History, 19th Century; D006801:Humans; D012586:Science / Q000266:history*