At first, in the time generally called the honeymoon, the unaccustomed freedom and the sweetness of the relation often does bring real happiness. How long does it last? Too often a far shorter time than is generally acknowledged. In the first joy of their union it is hidden from the two young people that they know little or nothing about the fundamental laws of each other's being. Much of the sex-attraction (not only among human beings, but even throughout the whole world of living creatures) depends upon the differences between the two that pair; and probably taking them all unawares, those very differences which drew them together now begin to work their undoing. But so long as the first illusion that each understands the other is supported by the thrilling delight of ever-fresh discoveries, the sensations lived through are so rapid and so joyous that the lovers do not realise that there is no firm foundation of real mutual knowledge beneath their feet. While even the happiest pair may know of divergencies about religion, politics, social custom, and opinions on things in general, these, with goodwill, patience, and intelligence on either side, can be ultimately adjusted, because in all such things there is a common meeting ground for the two. Human beings, while differing widely about every conceivable subject in such human relations, have at least _thought_ about them, threshed them out, and discussed them openly for generations. But about the much more fundamental and vital problems of sex, there is a lack of knowledge so abysmal and so universal that its mists and shadowy darkness have affected even the few who lead us, and who are prosecuting research in these subjects. And the two young people begin to suffer from fundamental divergencies, before perhaps they realise that such exist, and with little prospect of ever gaining a rational explanation of them. Nearly all those whose own happiness seems to be dimmed or broken count themselves exceptions, and comfort themselves with the thought of some of their friends, who, they feel sure, have attained the happiness which they themselves have missed. It is generally supposed that happy people, like happy nations, have no history--they are silent about their own affairs. Those who talk about their marriage are generally those who have missed the happiness they expected. True as this may be in general, it is not permanently and profoundly true, and there are people who are reckoned, and still reckon themselves, happy, but who yet unawares reveal the secret disappointment which clouds their inward peace. Leaving out of account "_femmes incomprises_" and all the innumerable neurotic, super-sensitive, and slightly abnormal people, it still remains an astonishing and tragic fact that so large a proportion of marriages lose their early bloom and are to some extent unhappy.