Ideology of Purity challenges the assumption that animal breeding has served as a reliable model for eugenics through a direct comparison of the views of eugenicists with those of animal breeders.

Eugenicists have cited animal breeding to justify their conceptions on human heredity and purity, misunderstanding the true meaning behind these principles and practices. Rather than accepting eugenic rhetoric at face value, this book examines how concepts like purity have been understood and applied differently in animal breeding and human eugenics. It explores how government policies have responded to both groups and aligned their demands. Historian Margaret E. Derry shows that the state promoted different forms of “purity” for animals and humans, and that the perceived parallels were more rhetorical than real. Through an analysis of topics such as nature versus nurture and the role of selective breeding, this book uncovers fundamental differences in goals, methods, and assumptions surrounding breeding. By drawing the conclusion that connections between eugenics and animal breeding were largely constructed through suggestive language rather than substantive similarity, Derry offers a new and critical perspective on the historical relationship between science, ideology, and policy.