On October 4, 1903, Otto Weininger died by his own hand, at the age of twenty-three and a half years. There is perhaps in all history no other instance of a man who had produced a work so mature in its scientific character, and so original in its philosophical aspect as "Sex and Character" when he was no more than twenty-one years old. We will not attempt to decide whether this was the case of a genius, who, instead of developing his intellectual powers gradually in the course of a lifetime, concentrated them in one mighty achievement, and then cast off the worn-out husk of the flesh, or of an unhappy youth, who could no longer bear the burden of his own ghastly knowledge."Sex and Character" is undoubtedly one of those rare books that will be studied long after its own times, and whose influence will not pass away, but will penetrate deeper and deeper, compelling amazement and inviting reflection in steadily expanding circles.