So accustomed have we recently become to accept one aspect of organic evolution, that we tend to see in youth only a recapitulation of our race's history. The well-worn phrase "Ontogeny repeats Phylogeny" has helped to concentrate our attention on the fact that the young in their development, in ourselves as in the animals, go through many phases which resemble the stages through which the whole race must have passed in the course of its evolution. While this is true, there is another characteristic of youth: It is prophetic! The dreams of youth, which each young heart expects to see fulfilled in its own life, seem so often to fade unfulfilled. But that is because the wonderful powers of youth are not supplied with the necessary tool--knowledge. And so potentialities, which could have worked miracles, are allowed to atrophy and die. But as humanity orients itself more truly, more and more will the knowledge and experience of the whole race be placed at the disposal of all youth on its entry into life. Then that glorious upspringing of the racial ideal, which finds its expression in each unspoiled generation of youth, will at last meet with a store of knowledge sufficient for its needs, and will find ready as a tool to its hand the accumulated and sifted wisdom of the race. Then youth will be spared the blunders and the pain and the unconscious self-destruction that to-day leaves scarcely anyone untouched. In my own life, comparatively short and therefore lacking in experience though it be, I have known both personally and vicariously so much anguish that might have been prevented by knowledge. This impels me not to wait till my experience and researches are complete, and my life and vital interest are fading, but to hand on at once those gleanings of wisdom I have already accumulated which may help the race to understand itself. Hence I conclude this little book, for, though incomplete, it contains some of the vital things youth should be told. In all life activities, house-building, hunting or any other, where intellectual and oral tradition comes in, as it does with the human race, "instinct" tends to die out. Thus the human mother is far less able to manage her baby without instruction than is a cat her kittens; although the human mother at her best has, in comparison with the cat, an infinitude of duties toward, and influences over, her child. A similar truth holds in relation to marriage. The century-long following of various "civilised" customs has not only deprived our young people of most of the instinctive knowledge they might have possessed, but has given rise to innumerable false and polluting customs. Though many write on the art of managing children, few have anything to say about the art of marriage, save those who have some dogma, often theological or subversive of natural law, to proclaim.