Because, for instance, love is based on an illusion and represents what is an advantage to the species as an advantage to the individual, the illusion necessarily vanishes directly the end of the species has been attained. The spirit of the species, which for the time being has got the individual into its possession, now frees him again. Deserted by the spirit, he relapses into his original state of narrowness and want; he is surprised to find that after all his lofty, heroic, and endless attempts to further his own pleasure he has obtained but little; and contrary to his expectation, he finds that he is no happier than he was before. He discovers that he has been the dupe of the will of the species. Therefore, as a rule, a Theseus who has been made happy will desert his Ariadne. If Petrarch's passion had been gratified his song would have become silent from that moment, as that of the birds as soon as the eggs are laid.
Let it be said in passing that, however much my metaphysics of love may displease those in love, the fundamental truth revealed by me would enable them more effectually than anything else to overcome their passion, if considerations of reason in general could be of any avail. The words of the comic poet of ancient times remain good: Quae res in se neque consilium, neque modum habet ullum, eam consilio regere non potes. People who marry for love do so in the interest of the species and not of the individuals. It is true that the persons concerned imagine they are promoting their own happiness; but their real aim, which is one they are unconscious of, is to bring forth an individual which can be begotten by them alone. This purpose having brought them together, they ought henceforth to try and make the best of things. But it very frequently happens that two people who have been brought together by this instinctive illusion, which is the essence of passionate love, are in every other respect temperamentally different. This becomes apparent when the illusion wears off, as it necessarily must.
Accordingly, people who marry for love are generally unhappy, for such people look after the welfare of the future generation at the expense of the present. Quien se casa por amores, ha de vivir con dolores (He who marries for love must live in grief), says the Spanish proverb. Marriages de convenance, which are generally arranged by the parents, will turn out the reverse. The considerations in this case which control them, whatever their nature may be, are at any rate real and unable to vanish of themselves. A marriage of this kind attends to the welfare of the present generation to the detriment of the future, it is true; and yet this remains problematical.
A man who marries for money, and not for love, lives more in the interest of the individual than in that of the species; a condition exactly opposed to truth; therefore it is unnatural and rouses a certain feeling of contempt. A girl who against the wish of her parents refuses to marry a rich man, still young, and ignores all considerations of convenance, in order to choose another instinctively to her liking, sacrifices her individual welfare to the species. But it is for this very reason that she meets with a certain approval, for she has given preference to what was more important and acted in the spirit of nature (of the species) more exactly; while the parents advised only in the spirit of individual egoism.
As the outcome of all this, it seems that to marry means that either the interest of the individual or the interest of the species must suffer. As a rule one or the other is the case, for it is only by the rarest and luckiest accident that convenance and passionate love go hand in hand. The wretched condition of most persons physically, morally, and intellectually may be partly accounted for by the fact that marriages are not generally the result of pure choice and inclination, but of all kinds of external considerations and accidental circumstances. However, if inclination to a certain degree is taken into consideration, as well as convenience, this is as it were a compromise with the genius of the species. As is well known, happy marriages are few and far between, since marriage is intended to have the welfare of the future generation at heart and not the present.
However, let me add for the consolation of the more tender-hearted that passionate love is sometimes associated with a feeling of quite another kind—namely, real friendship founded on harmony of sentiment, but this, however, does not exist until the instinct of sex has been extinguished. This friendship will generally spring from the fact that the physical, moral, and intellectual qualities which correspond to and supplement each other in two individuals in love, in respect of the child to be born, will also supplement each other in respect of the individuals themselves as opposite qualities of temperament and intellectual excellence, and thereby establish a harmony of sentiment.
The whole metaphysics of love which has been treated here is closely related to my metaphysics in general, and the light it throws upon this may be said to be as follows.
We have seen that a man's careful choice, developing through innumerable degrees to passionate love, for the satisfaction of his instinct of sex, is based upon the fundamental interest he takes in the constitution of the next generation. This overwhelming interest that he takes verifies two truths which have been already demonstrated.
First: Man's immortality, which is perpetuated in the future race. For this interest of so active and zealous a nature, which is neither the result of reflection nor intention, springs from the innermost characteristics and tendencies of our being, could not exist so continuously or exercise such great power over man if the latter were really transitory and if a race really and totally different to himself succeeded him merely in point of time.
Second: That his real nature is more closely allied to the species than to the individual. For this interest that he takes in the special nature of the species, which is the source of all love, from the most fleeting emotion to the most serious passion, is in reality the most important affair in each man's life, the successful or unsuccessful issue of which touches him more nearly than anything else. This is why it has been pre-eminently called the "affair of the heart." Everything that merely concerns one's own person is set aside and sacrificed, if the case require it, to this interest when it is of a strong and decided nature. Therefore in this way man proves that he is more interested in the species than in the individual, and that he lives more directly in the interest of the species than in that of the individual.