In this powerful critique, the esteemed historian and philosopher of science Evelyn Fox Keller addresses the nature-nurture debates, including the persistent disputes regarding the roles played by genes and the environment in determining individual traits and behavior. Keller is interested in both how an oppositional “versus” came to be inserted between nature and nurture, and how the distinction on which that opposition depends, the idea that nature and nurture are separable, came to be taken for granted. How, she asks, did the illusion of a space between nature and nurture become entrenched in our thinking, and why is it so tenacious? Keller reveals that the assumption that the influences of nature and nurture can be separated is neither timeless nor universal, but rather a notion that emerged in Anglo-American culture in the late nineteenth century. She shows that the seemingly clear-cut nature-nurture debate is riddled with incoherence. It encompasses many disparate questions knitted together into an indissoluble tangle, and it is marked by a chronic ambiguity in language. There is little consensus about the meanings of terms such as nature, nurture, gene, and environment. Keller suggests that contemporary genetics can provide a more appropriate, precise, and useful vocabulary, one that might help put an end to the confusion surrounding the nature-nurture controversy.