After reading a review in The New Yorker about Daniel Brook’s new biography of Dr. Magnus Hirschfeld, I felt compelled to purchase and read the book. Why? I’m the proud father of a transgender 21-year-old woman who came out to her mom and me in high school. I didn’t react perfectly in that moment — I didn’t yet understand what she needed to hear. Years of reading and learning about sexuality and gender have shown me that identity exists on a spectrum, and much of that understanding traces back to Dr. Magnus Hirschfeld at the turn of the 20th century.
Daniel Brook’s The Einstein of Sex offers a vivid, accessible portrait of the German-Jewish physician whose groundbreaking work reshaped early 20th-century thinking on sexuality, gender, and civil rights. Brook follows Hirschfeld’s development from his Prussian upbringing to becoming one of Europe’s boldest medical thinkers. In 1896, Hirschfeld published his first gay-rights pamphlet asserting that sexual orientation existed along a spectrum — a radical idea for its time. Over the next decade, he expanded this view, proposing that every person carries a mix of masculine and feminine traits. This framework opened the door to thinking about transgender identity long before the language existed.
Brook shows how Hirschfeld’s science and activism were intertwined. He founded the Scientific-Humanitarian Committee in 1897, the world’s first LGBTQ-rights organization, and spent decades fighting Paragraph 175, the German law criminalizing sex between men. His pamphlet What People Should Know About the Third Sex appealed to logic, empathy, and justice, arguing that same-sex love was equally capable of purity and nobility.
In 1919, Hirschfeld established the Institute for Sexual Science, home to the first gender-affirming surgeries, a global research library, and a museum that became a celebrated Weimar destination. As a public figure, he appeared in newsreels, lectured worldwide, and used his influence to advocate for inclusion in the military, medicine, and public life.
His travels strengthened his belief that identity — including race — is relative rather than fixed. In exile, he observed how different societies placed him in inconsistent racial categories, reinforcing his view that race was a social invention, not a biological fact. This embrace of relativity, echoed in his theories of sex and gender, earned him the moniker “Einstein of Sex,” a comparison he accepted with some reluctance.
As Brook documents, the Nazis targeted Hirschfeld relentlessly, nearly killed him, destroyed his institute, and burned his books in 1933. Though his life’s work was nearly erased, his ideas endured. Hirschfeld’s message remains strikingly relevant as today’s debates over gender, sexuality, censorship, and rising authoritarianism mirror the tensions of his era. Brook’s book reintroduces readers to the Hirschfeld Scale, his insistence on the fluid nature of identity, and his belief in the dignity of queer and trans lives.
My verdict: The Einstein of Sex is well worth reading — whether you’re part of the LGBTQ+ community, an ally, or simply someone seeking to better understand the science of sex and gender.
Sources:
https://www.newyorker.com/magazine/2025/10/06/the-einstein-of-sex-stan-and-gus-heart-the-lover-muscle-man
https://www.amazon.com/Einstein-Sex-Magnus-Hirschfeld-Visionary/dp/1324007249/ref=sr_1_1?crid=1DZSRAE2IS7Q6&dib=eyJ2IjoiMSJ9.QLLohB_pvDrmg-I1BuKKiw.7TqeHSjRv92Wzasrb6bheZIs9pp5sX43q5OWoZ7IXls&dib_tag=se&keywords=the+einstein+of+sex+by+daniel+brook&qid=1763845313&sprefix=The+Einstein+of+Sex+%2Caps%2C130&sr=8-1
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