Now that Summers has released the text of his January 14 speech, we can see that he presented three very rational hypotheses to explain why there are fewer women than men in science and engineering academia: (1) “the high-powered job hypothesis” (the concept that women voluntarily reject the 80-hour-week and job-intensity that top careers require), (2) “different availability of aptitude at the high end,” and (3) “different socialization and patterns of discrimination” (the favorite feminist explanation for all sex differences).