Weininger equates women with nothing.
Nothing is Chaos, which is both A and Not-A existing at the same time. So that means that there are options, but no choices. Will is required to make a choice. Will exerts itself on Options and chooses one or the other, A or Not-A. Chaos is the foundation on which the cosmos is built. It's reflected in quantum mechanics, in that things exist and dont exist. The supposed Physical Laws of the Universe have no authority down there. It is only Will that makes a choice of the Options extant in Chaos. Woman is Chaos. Options but not choice.
Sex and Character, page 191 
I am now ready to answer the question which I put forward as the chief object of
this portion of my book, the question as to the significance of the male and female in
the universe. Women have no existence and no essence; they are not, they are
nothing. Mankind occurs as male or female, as something or nothing. Woman has no
share in ontological reality, no relation to the thing-in-itself, which, in the deepest
interpretation, is the absolute, is God. Man in his highest form, the genius, has such a
relation, and for him the absolute is either the conception of the highest worth of
existence, in which case he is a philosopher; or it is the wonderful fairyland of
dreams, the kingdom of absolute beauty, and then he is an artist. But both views mean
the same. Woman has no relation to the idea, she neither affirms nor denies it; she is
neither moral nor antimoral; mathematically speaking, she has no sign; she is
purposeless, neither good nor bad, neither angel nor devil, never egoistical (and
therefore has often been said to be altruistic); she is as nonmoral as she is nonlogical.
But all existence is moral and logical existence. So woman has no existence.