Outward manifestation of instinct can be best observed in animals, where the part it plays is most significant; but it is in ourselves alone that we can get to know its internal process, as of everything internal. It is true, it is thought that man has scarcely any instinct at all, or at any rate has only sufficient instinct when he is born to seek and take his mother's breast. But as a matter of fact man has a very decided, clear, and yet complicated instinct—namely, for the selection, both earnest and capricious, of another individual, to satisfy his instinct of sex. The beauty or ugliness of the other individual has nothing whatever to do with this satisfaction in itself, that is in so far as it is a matter of pleasure based upon a pressing desire of the individual. The regard, however, for this satisfaction, which is so zealously pursued, as well as the careful selection it entails, has obviously nothing to do with the chooser himself, although he fancies that it has. Its real aim is the child to be born, in whom the type of the species is to be preserved in as pure and perfect a form as possible. For instance, different phases of degeneration of the human form are the consequences of a thousand physical accidents and moral delinquencies; and yet the genuine type of the human form is, in all its parts, always restored; further, this is accomplished under the guidance of the sense of beauty, which universally directs the instinct of sex, and without which the satisfaction of the latter would deteriorate to a repulsive necessity.
Accordingly, every one in the first place will infinitely prefer and ardently desire those who are most beautiful—in other words, those in whom the character of the species is most purely defined; and in the second, every one will desire in the other individual those perfections which he himself lacks, and he will consider imperfections, which are the reverse of his own, beautiful. This is why little men prefer big women, and fair people like dark, and so on. The ecstasy with which a man is filled at the sight of a beautiful woman, making him imagine that union with her will be the greatest happiness, is simply the sense of the species. The preservation of the type of the species rests on this distinct preference for beauty, and this is why beauty has such power.
We will later on more fully state the considerations which this involves. It is really instinct aiming at what is best in the species which induces a man to choose a beautiful woman, although the man himself imagines that by so doing he is only seeking to increase his own pleasure. As a matter of fact, we have here an instructive solution of the secret nature of all instinct which almost always, as in this case, prompts the individual to look after the welfare of the species. The care with which an insect selects a certain flower or fruit, or piece of flesh, or the way in which the ichneumon seeks the larva of a strange insect so that it may lay its eggs in that particular place only, and to secure which it fears neither labour nor danger, is obviously very analogous to the care with which a man chooses a woman of a definite nature individually suited to him. He strives for her with such ardour that he frequently, in order to attain his object, will sacrifice his happiness in life, in spite of all reason, by a foolish marriage, by some love-affair which costs him his fortune, honour, and life, even by committing crimes. And all this in accordance with the will of nature which is everywhere sovereign, so that he may serve the species in the most efficient manner, although he does so at the expense of the individual.
Instinct everywhere works as with the conception of an end, and yet it is entirely without one. Nature implants instinct where the acting individual is not capable of understanding the end, or would be unwilling to pursue it. Consequently, as a rule, it is only given prominently to animals, and in particular to those of the lowest order, which have the least intelligence. But it is only in such a case as the one we are at present considering that it is also given to man, who naturally is capable of understanding the end, but would not pursue it with the necessary zeal—that is to say, he would not pursue it at the cost of his individual welfare. So that here, as in all cases of instinct, truth takes the form of illusion in order to influence the will....
All this, however, on its part throws light upon the instinct of animals. They, too, are undoubtedly carried away by a kind of illusion, which represents that they are working for their own pleasure, while it is for the species that they are working with such industry and self-denial. The bird builds its nest; the insect seeks a suitable place wherein to lay its eggs, or even hunts for prey, which it dislikes itself, but which must be placed beside the eggs as food for the future larvae; the bee, the wasp, and the ant apply themselves to their skilful building and extremely complex economy. All of them are undoubtedly controlled by an illusion which conceals the service of the species under the mask of an egotistical purpose.
This is probably the only way in which to make the inner or subjective process, from which spring all manifestations of instinct, intelligible to us. The outer or objective process, however, shows in animals strongly controlled by instinct, as insects for instance, a preponderance of the ganglion—i.e., subjective nervous system over the objective or cerebral system. From which it may be concluded that they are controlled not so much by objective and proper apprehension as by subjective ideas, which excite desire and arise through the influence of the ganglionic system upon the brain; accordingly they are moved by a certain illusion....
The great preponderance of brain in man accounts for his having fewer instincts than the lower order of animals, and for even these few easily being led astray. For instance, the sense of beauty which instinctively guides a man in his selection of a mate is misguided when it degenerates into the proneness to pederasty. Similarly, the blue-bottle (Musca vomitoria), which instinctively ought to place its eggs in putrified flesh, lays them in the blossom of the Arum dracunculus, because it is misled by the decaying odour of this plant. That an absolutely generic instinct is the foundation of all love of sex may be confirmed by a closer analysis of the subject—an analysis which can hardly be avoided.
In the first place, a man in love is by nature inclined to be inconstant, while a woman constant. A man's love perceptibly decreases after a certain period; almost every other woman charms him more than the one he already possesses; he longs for change: while a woman's love increases from the very moment it is returned. This is because nature aims at the preservation of the species, and consequently at as great an increase in it as possible.... This is why a man is always desiring other women, while a woman always clings to one man; for nature compels her intuitively and unconsciously to take care of the supporter and protector of the future offspring. For this reason conjugal fidelity is artificial with the man but natural to a woman. Hence a woman's infidelity, looked at objectively on account of the consequences, and subjectively on account of its unnaturalness, is much more unpardonable than a man's.
In order to be quite clear and perfectly convinced that the delight we take in the other sex, however objective it may seem to be, is nevertheless merely instinct disguised, in other words, the sense of the species striving to preserve its type, it will be necessary to investigate more closely the considerations which influence us in this, and go into details, strange as it may seem for these details to figure in a philosophical work. These considerations may be classed in the following way:—
Those that immediately concern the type of the species, id est, beauty; those that concern other physical qualities; and finally, those that are merely relative and spring from the necessary correction or neutralisation of the one-sided qualities and abnormities of the two individuals by each other. Let us look at these considerations separately.