Up to the present I have taken into consideration merely the absolute considerations—­id est, such considerations as apply to every one.  I now come to the relative considerations, which are individual, because they aim at rectifying the type of the species which is defectively presented and at correcting any deviation from it existing in the person of the chooser himself, and in this way lead back to a pure presentation of the type.  Hence each man loves what he himself is deficient in.  The choice that is based on relative considerations—­that is, has in view the constitution of the individual—­is much more certain, decided, and exclusive than the choice that is made after merely absolute considerations; consequently real passionate love will have its origin, as a rule, in these relative considerations, and it will only be the ordinary phases of love that spring from the absolute.  So that it is not stereotyped, perfectly beautiful women who are wont to kindle great passions.  Before a truly passionate feeling can exist, something is necessary that is perhaps best expressed by a metaphor in chemistry—­namely, the two persons must neutralise each other, like acid and alkali to a neutral salt.  Before this can be done the following conditions are essential.  In the first place, all sexuality is one-sided.  This one-sidedness is more definitely expressed and exists in a higher degree in one person than in another; so that it may be better supplemented and neutralised in each individual by one person than by another of the opposite sex, because the individual requires a one-sidedness opposite to his own in order to complete the type of humanity in the new individual to be generated, to the constitution of which everything tends....

The following is necessary for this neutralisation of which we are speaking.  The particular degree of his manhood must exactly correspond to the particular degree of her womanhood in order to exactly balance the one-sidedness of each.  Hence the most manly man will desire the most womanly woman, and vice versa, and so each will want the individual that exactly corresponds to him in degree of sex.  Inasmuch as two persons fulfil this necessary relation towards each other, it is instinctively felt by them and is the origin, together with the other relative considerations, of the higher degrees of love.  While, therefore, two lovers are pathetically talking about the harmony of their souls, the kernel of the conversation is for the most part the harmony concerning the individual and its perfection, which obviously is of much more importance than the harmony of their souls—­which frequently turns out to be a violent discord shortly after marriage.

We now come to those other relative considerations which depend on each individual trying to eradicate, through the medium of another, his weaknesses, deficiencies, and deviations from the type, in order that they may not be perpetuated in the child that is to be born or develop into absolute abnormities.  The weaker a man is in muscular power, the more will he desire a woman who is muscular; and the same thing applies to a woman....