"On the Basis of ___" (film about Ruth Bader Ginsburg)

I believe the answer is:

sex

(Other definitions for sex that I've seen before include "Hanky-panky" , "Expert in the treatment of coital problems" , "Gender" , "Male or female" , "VI (Lat.); m. or f." .)

I've seen this clue in The New York Times.

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