...suppose as a woman and a Kantian you take your role as a progenitor of a future line of human descent quite seriously. You want to become a mother. Perfectly aware that this is an instinct but also believing without hesitation that it is a good thing to bring life into the world, that it is a moral act, perhaps as morally good as an act of taking life is morally bad. Being an attractive woman you know that you shall not have to work hard at persuading a male to impregnate you. You know, however, you have no business using your mere attractiveness to him for this admittedly good purpose or for encouraging him to permit himself to be used for any other reason than that he also sees good in the act of engendering life. Suppose further you find such a man who shares your view of the matter, who admits his attraction to you, but earnestly struggles against it in the interest of not using you and not allowing himself to be used by you. (Incidentally, any kind of artificial insemination or in vitro fertilization, because these are not moral occasions, is also out of the question. Moral occasions occur only when improvable humans interact.)
We have to ask why you think it is a good thing to bring life into the world apart from any inclination you may have to do so? So that there may be new opportunities for human improvement? Surely not that there be new opportunities for enjoyment since whatever enjoyment beings like us may derive from being alive is incidental, if not a hindrance, to our purpose here. Surely not that there be new opportunities for misery since that as well is immaterial to our mission. If it is for the refinement of our rational capacity, we must notice that what does not exist cannot very well stand being made better. The case is credible that given our existence and rational capacity, we may indeed have such a mandate. But why more like us? Why does reason need them? When the last of us passes into oblivion, or wherever rational agents go when they die, will reason miss us?
Weininger thought not. And contrary to what some of you may be muttering, he thought the joke was on us, not reason. This is not a reductio of Kantian morality but its vindication. It is in the end inscrutable to thought guided by inclination that reason might be autonomous.
—from Luno's Notes and Meditations on Weininger