Last week, Sports Illustrated ran a profile of Lia Thomas, the male swimmer setting records as a member of the University of Pennsylvania women’s swim team. SI reporter Robert Sanchez called Thomas “one of the most dominant college athletes in the country” and “a living, breathing, real-time Rorschach test for how society views those who challenge conventions.” He is kind of like Jackie Robinson in that way.

Thomas set several school and Ivy League women’s swimming records this year and is poised to break national marks at the NCAA championship in March. To get a sense of his dominance, watch Thomas lap the second-place finisher in a race last year.

One must feel a degree of sympathy for Thomas. No one takes cross-sex hormones without feeling significant anguish.

That does not entitle him to participate in a women’s sport, however, and the reason it does not—and we must be precise about this—is not because he has a biological advantage over his female competitors, which he does, and not because he is a relatively fast swimmer, which he is, but because he is not a woman.

Lia Thomas could be the slowest swimmer at the University of Pennsylvania, and it would not at all change the substance of the issue. Debates about women’s sports are a useful way to address the differences between men and women, because those differences are obvious in the athletic context. But “fairness” is not the primary reason to bar Thomas from participating in women’s sports, and neither is the supposed imperative to “preserve and protect women’s sports.” The effects of puberty on athletic performance, the extent to which hormone replacement therapy can reverse those effects, and the relative importance of fairness and inclusion in sports are each secondary considerations. Thomas himself identifies the crux of the matter.

A Penn parent interviewed in the SI profile, who uses feminine pronouns to describe Thomas and “identifies as a progressive,” opposes Thomas’s participation in women’s sports on fairness grounds. “Lia is a human being who deserves to be treated with respect and dignity,” the parent said. “But it’s not transphobic to say I disagree with where she’s swimming.”

Thomas found the parent’s argument “disingenuous.”

“The very simple answer is that I’m not a man,” Thomas said in response. “I’m a woman, so I belong on the women’s team.”