Argues that intoxication was fundamental to German physiological, psychological, and psychiatric research during the nineteenth century. Intoxicating substances can be found lurking in every corner of modern life, and Matthew Perkins-McVey’s pathbreaking book offers the untold story of how they were implicated in shifting perceptions of embodiment found in the emerging sciences of the body and mind in late-nineteenth-century Germany. Their use in this experimental context gave rise to a dynamic conception of the subject within the scientific, psychological, philosophical, and sociological milieu of the era. The history of the modern biological subject, Perkins-McVey argues, turns on “intoxicated ways of knowing.” Intoxicated Ways of Knowing identifies the state of intoxication as a tacit form of thinking and knowing with the body. Intoxicants force us to feel, intervening directly in our perceptional awareness, and, Perkins-McVey contends, they bring latent conceptual associations into the foreground of conscious thought, engendering new ways of knowing the world. The book unfurls how intoxicants affected nineteenth-century German science and how, ultimately, the connection between mental life and intoxication is taken up in the works of Friedrich Nietzsche, Max Weber, and Sigmund Freud, bringing the biological subject out of the lab and into the worlds of philosophy, psychoanalysis, sociology, and politics.