German-Jewish physician, sexologist and critical race theorist Magnus Hirschfeld (1868–1935) was arguably one of the most significant sexual thinkers of the twentieth century and a renowned sexual minority rights advocate. Hirschfeld’s sexual- emancipatory engagement has been widely acknowledged. But his groundbreaking universalization of sexual intermediariness and the resulting dissolution of binary, triadic or otherwise finite schemes of sexuality have been mostly ignored or misrepresented in intellectual history. A relevant exception in this regard is the way sexuality historian Manfred Herzer has shortly approached the “doctrine of sexual intermediaries” as the “key concept” of his thought. While assessing and setting in historical perspective Herzer’s interpretive contentions, the present study foregrounds Hirschfeld’s Darwinian-inspired, non-essentialist naturalism as the ontic support for the new sexual and race regime he envisaged. By conceptualizing the potential in-finitization of sexualities and races, Hirschfeld was envisioning an unprecedented path toward the Messianic—albeit a-theological—goal of intra-historic liberation.