The Book of Minor Perverts: Sexology, Etiology, and the Emergences of Sexuality theorizes a historical etiological method as an alternative to the epistemological approaches that play such a vital role in the field-imaginary of sexuality studies. This historical etiological approach recovers a multiplicity of patterns, models, and categories of sexuality, recording their sites of production, tracing synchronic relations between sexual formations, and theorizing the contours of these sexualities by attending to the accounts of their origins. At its broadest, this project seeks not to rationalize what Eve Sedgwick calls “the unrationalized coexistence of different models” of sexuality, but to understand how their coexistence occurred. This book contends that historical etiology is a crucial tool — if not the crucial tool — for periodizing and narrativizing the invention of sexuality. It provides an account of the process by which the gender of object choice becomes the basis of classification and definition for sexuality and a description of the simultaneous speciation of what Michel Foucault calls “minor perverts” who fit “no order”: zoophiles, zooerasts, auto-monosexualists, and numberless more. These minor perverts bring into focus largely vestigial models of sexuality, making visible the formation of and competition between different models of sexuality and helping us to imagine it otherwise.