Iwan Bloch was a German dermatologist and pioneering researcher in sexual anomalies. Instrumental in formalizing the discipline of sexology, which upheld the biological basis of sexual phenomena, he revolutionized sexology by integrating cultural and anthropological insights into medical theories of sexual life. Bloch's research upheld the naturalness of sexual variety and argued against scientific theories that classified sexual anomalies as perversions. His 150 publications include a groundbreaking cultural history of the Marquis de Sade, numerous sexual histories, and unprecedented scientific forays into sexual phenomena, including syphilis, prostitution, sadism, and impotence. Bloch was also an advocate of sexual reform and supported women's rights and the decriminalization of prostitution, abortion, and homosexuality.