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.