always directs the sexual impulse, and without which this sinks to the level of a disgusting necessity. Accordingly, in the first place, every one will decidedly prefer and eagerly desire the most beautiful individuals, _i.e._, those in whom the character of the species is most purely impressed; but, secondly, each one will specially regard as beautiful in another individual those perfections which he himself lacks, nay, even those imperfections which are the opposite of his own. Hence, for example, little men love big women, fair persons like dark, &c. &c. The delusive ecstasy which seizes a man at the sight of a woman whose beauty is suited to him, and pictures to him a union with her as the highest good, is just the _sense of the species_, which, recognising the distinctly expressed stamp of the same, desires to perpetuate it with this individual. Upon this decided inclination to beauty depends the maintenance of the type of the species: hence it acts with such great power. We shall examine specially further on the considerations which it follows. Thus what guides man here is really an instinct which is directed to doing the best for the species, while the man himself imagines that he only seeks the heightening of his own pleasure. In fact, we have in this an instructive lesson concerning the inner nature of all instinct, which, as here, almost always sets the individual in motion for the good of the species. For clearly the pains with which an insect seeks out a particular flower, or fruit, or dung, or flesh, or, as in the case of the ichneumonidæ, the larva of another insect, in order to deposit its eggs there only, and to attain this end shrinks neither from trouble nor danger, is thoroughly analogous to the pains with which for his sexual satisfaction a man carefully chooses a woman with definite qualities which appeal to him individually, and strives so eagerly after her that in order to attain this end he often sacrifices his own happiness in life, contrary to all reason, by a foolish marriage, by love affairs which cost him wealth, honour, and life, even by crimes such as adultery or rape, all merely in order to serve the species in the most efficient way, although at the cost of the individual, in accordance with the will of nature which is everywhere sovereign. Instinct, in fact, is always an act which seems to be in accordance with the conception of an end, and yet is entirely without such a conception. Nature implants it wherever the acting individual is incapable of understanding the end, or would be unwilling to pursue it. Therefore, as a rule, it is given only to the brutes, and indeed especially to the lowest of them which have least understanding; but almost only in the case we are here considering it is also given to man, who certainly could understand the end, but would not pursue it with the necessary ardour, that is, even at the expense of his individual welfare.