Otto Weininger was born on April 3, 1880, in Vienna as a son of the Jewish goldsmith Leopold Weininger and his wife Adelheid. After attending primary school and graduating from secondary school in July 1898, Weininger registered at the University of Vienna in October of the same year. He studied philosophy and psychology but took courses in natural sciences and medicine as well. Weininger learned Greek, Latin, French and English very early, later also Spanish and Italian, and acquired passive knowledge of the languages of August Strindberg and Henrik Ibsen (i.e., Swedish and Danish/Norwegian).
In the autumn of 1901 Weininger tried to find a publisher for his work Eros and the Psyche – which he submitted to his professors Friedrich Jodl and Laurenz Mullner as his thesis in 1902. He met Sigmund Freud, who, however, did not recommend the text to a publisher. His professors accepted the thesis and Weininger received his Ph.D. degree in July 1902. Shortly thereafter he became proudly and enthusiastically a Protestant.
In 1902 Weininger went to Bayreuth where he witnessed a performance of Richard Wagner's Parsifal, which left him deeply impressed. Via Dresden and Copenhagen he made his way to Christiania (Oslo) where he for the first time saw Henrik Ibsen's liberation drama Peer Gynt on stage. Upon his return to Vienna Weininger suffered from fits of deep depression. The decision to take his own life gradually took shape in his mind; after a long discussion with his friend Artur Gerber, however, Weininger realized that "it is not yet time".
In June 1903, after months of concentrated work, his book Sex and Character – A Fundamental Investigation – an attempt "to place sex relations in a new and decisive light" – was published by the Vienna publishers Braumuller & Co. The book contained his thesis to which three vital chapters were added: (XII) "The Nature of Woman and her Relation to the Universe", (XIII) "Judaism", (XIV) "Women and Humanity".
While the book was not received negatively, it did not create the expected stir. Weininger was attacked by Paul Julius Mobius, professor in Leipzig and author of the book On the Physiological Deficiency of Women, and was accused of plagiarizing. Deeply disappointed and seemingly depressed, Weininger left for Italy.
Back in Vienna he spent his last five days with his parents. On October 3, he took a room in the house in Schwarzspanierstrase 15 where Ludwig van Beethoven died. He told the landlady that he was not to be disturbed before morning since he planned to work and then to go to bed late. This night he wrote two letters, one addressed to his father, the other one to his brother Richard, telling them that he was going to shoot himself.
On October 4, Weininger was found mortally wounded, having shot himself through the heart. He died in the Wiener Allgemeines Krankenhaus (Vienna general hospital) at half past ten that morning. Otto Weininger was buried in the Matzleinsdorf Protestant Cemetery in Vienna. The epitaph by his father translates:
This stone marks the resting place of a youth whose spirit never found rest on earth. And when he had made known the revelations of his spirit and of his soul, he could no longer bear to be among the living. He sought out the place of death of an Eternal Great in Vienna's Schwarzspanier House, and there destroyed his bodily existence.
Sex and Character argues that all people are composed of a mixture of male and the female substance, and attempts to support his view scientifically. The male aspect is active, productive, conscious and moral/logical, while the female aspect is passive, unproductive, unconscious and amoral/alogical. Weininger argues that emancipation is only possible for the "masculine woman", e.g. some lesbians, and that the female life is consumed with the sexual function: both with the act, as a prostitute, and the product, as a mother. Woman is a "matchmaker". By contrast, the duty of the male, or the masculine aspect of personality, is to strive to become a genius, and to forgo sexuality for an abstract love of the absolute, God, which he finds within himself.
A significant part of his book is about the nature of genius. Weininger argues that there is no such thing as a person who has a genius for, say, mathematics, or music, but there is only the universal genius, in whom everything exists and makes sense. He reasons that such genius is probably present in all people to some degree.
In a separate chapter, Weininger, himself a Jew who had converted to Christianity in 1902, analyzes the archetypal Jew as feminine, and thus profoundly irreligious, without true individuality (soul), and without a sense of good and evil. Christianity is described as "the highest expression of the highest faith", while Judaism is called "the extreme of cowardliness". Weininger decries the decay of modern times, and attributes much of it to feminine (or identically, "Jewish") influences. By Weininger's reckoning everyone shows some femininity, and what he calls "Jewishness".
Weininger's suicide in the house in Vienna, where Beethoven had died, the man he considered one of the greatest geniuses of all, made him a cause celebre, inspired several imitation suicides, and created a lot more interest in his book. The book received glowing reviews by August Strindberg, who wrote that it had "probably solved the hardest of all problems", the "woman problem".
Ludwig Wittgenstein read the book as a schoolboy and was deeply impressed by it, later listing it as one of his influences and recommending it to friends. However, Wittgenstein's deep admiration of Weininger's thought was coupled with a fundamental disagreement with his position. Wittgenstein writes to G. E. Moore: "It isn't necessary or rather not possible to agree with him but the greatness lies in that with which we disagree. It is his enormous mistake which is great." Elsewhere Wittgenstein put the same point by saying that if one were to add a negation sign before the whole of Sex and Character, one would have expressed a great truth; that is, he did not disagree with Weininger point by point but as a whole.
Weininger's friend Artur Gerber gave a description of Weiniger's physiognomy in "Ecce Homo", preface to Taschenbuch und Briefe an einen Freund (E. P. Tal & Co., Leipzig/Vienna 1922):
Nobody who had once seen his face could ever forget it. The big dome of his forehead marked it. The face was peculiar looking because of the large eyes; the look in them seemed to surround everything. In spite of his youth, his face was not handsome, it was rather ugly. Never did I see him laugh or smile. His face was always dignified and serious. Only when he was outdoors in spring did it seem to relax, and then become cheerful and bright. At many concerts he would shine with happiness. In the most wonderful moments we spent together, particularly when he talked about an idea in which he was interested, his eyes were filled with happiness. Otherwise his face was impenetrable. One could never—except to the last few months—find in his face any hint of what was happening deep within his soul. The taut muscles would often move, and sharp wrinkles would appear on his face, as if they were caused by intolerable pain. I asked for the reason, he controlled himself at once, gave a vague or evasive answer, or talked about other matters, making further questioning impossible.
His manners would occasionally elicit surprise, and often a smile, since he cared little for traditions and prejudices.
Isolated parts of Weininger's writings were used by Nazi propaganda, despite the fact that Weininger actively argued against the ideas of race that came to be identified with the Nazis:
A genius has perhaps scarcely ever appeared amongst the negroes, and the standard of their morality is almost universally so low that it is beginning to be acknowledged in America that their emancipation was an act of imprudence.
Greatness is absent from the nature of the woman and the Jew, the greatness of morality, or the greatness of evil. In the Aryan man, the good and bad principles of Kant’s religious philosophy are ever present, ever in strife. In the Jew and the woman, good and evil are not distinct from one another.