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Natural kind: gender is not a natural kind

Saul Kripke and Hilary Putnam showed how natural kinds work — water is H2O, tiger is a species. Woman as a biological category fits into that pattern. "Gender identity" is an empty collection that fills itself with whoever places themselves in it — and upon that nominal category rests the wiping away of the real category of woman.

What a natural kind is

In Naming and Necessity (1980), Kripke argued that some terms refer to real, distinct natural species with a hidden essence. Water = H2O, regardless of how it appears. Gold = atomic number 79. Tiger = a specific biological species. These categories are not socially invented; they have been discovered and persist regardless of what we think of them.

Woman as a natural kind

"Woman" — as a biological category — meets Kripke's criteria. There is a distinguishing feature: the female developmental pathway and the production of major gametes (see chromosomes and gametes ). Countless traits are causally linked to this: pregnancy, menarche, menopause, hormone profile, susceptibility to disease. This is not a social label but a biological class. See also biological sex and sex versus gender .

Gender identity as a pseudo-species

"Gender identity" lacks such a hidden essence. What is the "essence" of a female gender identity? No marker , no brain marker , no genetic marker , no distinguishing feature, no causal connection to other traits. The concept functions as an empty collection: it contains whoever places themselves within it. According to the argument of this article, that makes gender identity a non-natural kind in Kripke and Putnam's sense — rather a nominal category, based on circular reasoning .

The damage of category blurring

When "woman" is redefined to encompass everyone who identifies as a woman, the term is disconnected from its natural reference. Statisticians, doctors, and biologists are forced to designate two fundamentally different categories with a single word—which hinders communication, sports, childcare, care, and research. It is the legal erasure of the category of woman. In the foreword to the Cass Review (2024), Hilary Cass writes that the debate on this is exceptionally toxic and that professionals are afraid to openly discuss their views (source). See also language analysis and feminist criticism .