Not only is mere instinct not a good guide in the egoistic-social activities, but in the erotic life it is almost worse than useless. This is so because modern life is so different from the prehistoric environment that humans are today unable to follow erotic instinct, or even, on account of traditional inhibitions, to get at it in its purity. We live today in an environment so preponderantly egoistic-social that the majority of motives for any act are egoistic-social ones, and only a small fraction of them erotic. This makes it as difficult to follow erotic instincts as for a compass to point north, when a magnet is lying three inches to the east of it. Instinct alone would naturally prompt a boy and a girl to dwell long over the preliminaries to the love episode. If left together and alone, they would take some time to reach an erotic acme, and would instinctively find that out last of all, as is so beautifully described in Marlowe’s _Hero and Leander_, and so delicately suggested in _Paul and Virginia_. Not only has the social convention of the present day tended more and more to inhibit the introduction, prelude, first and second acts of the love drama but it has raised such a barrier against the third act as to give it an entirely disproportionate value in comparison with the others. § 56 There are three separate fusions involved in any perfect heterosexual union: (1) the bodily fusion of the man and the woman, (2) the fusion of their souls each with the other and (3) the fusion of the soul and body of each more closely together. The last comes from the man on his side and the woman on hers, each seeing the world more _sub specie Amoris_—as manifestation of erotic passion; but it also comes from the fact that the admission into consciousness of the innate erotic reactions, in spite of the opposition of environment—the legitimate admission of these feelings—vitalizes not only the physical body of man and woman, but also all the multitudinous and diversified contacts of both man and woman with people and things. Instinct alone, if it were possible to follow it unchecked, would lead to those three fusions; but the sex instinct in men and women has been so submerged by various forms of prohibition that even in the married state most husbands and wives do not know of the joy of any of these three fusions. § 57 One type of instinctive behaviour is the almost universal tendency to reason by analogy which frequently turns out to be a reasoning by false analogy and by association of the contiguity type. It would be quite as reasonable for a woman to say that, because a prostitute enjoys roast beef or lobster (or anything between), the pure wife should feel it a sin to enjoy good food.