as little guided by knowledge of the end as in mechanical instincts; in these also the will manifests itself, in the main, without the mediation of knowledge, which here, as there, is only concerned with details. Reproduction is, to a certain extent, the most marvellous of all instincts, and its work the most astonishing. These considerations explain why the sexual desire has a very different character from every other; it is not only the strongest, but even specifically of a more powerful kind than any other. It is everywhere tacitly assumed as necessary and inevitable, and is not, like other desires, a matter of taste and disposition. For it is the desire which even constitutes the nature of man. In conflict with it no motive is so strong that it would be certain of victory. It is so pre‐eminently the chief concern that no other pleasures make up for the deprivation of its satisfaction; and, moreover, for its sake both brute and man undertake every danger and every conflict. A very naïve expression of this disposition is the well‐known inscription on the door of the _fornix_ at Pompeii, decorated with the phallus: “_Heic habitat felicitas_:” this was for those going in naïve, for those coming out ironical, and in itself humorous. On the other hand, the excessive power of the sexual passion is seriously and worthily expressed in the inscription which (according to Theon of Smyrna, _De Musica_, c. 47), Osiris had placed upon the column he erected to the eternal gods: “To Eros, the spirit, the heaven, the sun, the moon, the earth, the night, the day, and the father of all that is and that shall be;” also in the beautiful apostrophe with which Lucretius begins his work: “_Æneadum genetrix, hominum divomque voluptas,_ _Alma Venus cet._”