PART II. How far our Happiness depends on Nature and Fate. I. _Our Bodily and Mental Constitutions._ To live happily, we must in the first place _live_. Transparent truism, but how often forgotten! How many of our pleasures tend to weaken life, rather than to strengthen and to lengthen it! Some philosophers have found the sense of existence a sufficient synonym for happiness. Sir William Hamilton expressed this opinion with perhaps an ambiguous under-meaning when he said,――“To lead a happy life is to live all the days of one’s life;” but Dr. Johnson, moralizing on the learned pig, expanded the idea more clearly when he maintained that the mere prolongation of existence is a sufficient compensation for a very considerable amount of suffering. We see the correctness of his observation in the multitude of examples of those who cherish their years when poverty, old age, and disease would seem to have robbed them of all value. When nothing else is left but life, life alone becomes worth all else. Self-preservation, therefore, which means the care of life and health, is the first and a necessary condition of personal happiness. But what a task is this! When the child wakes to consciousness and surveys the scene around him, he finds himself on a battle-field divided between two mighty combatants in unremitting conflict――Necessity and Chance, the laws of Nature and the caprices of Accident. Not even the gods, said the ancient Greeks, can struggle with Fate and Fortune, those elemental powers, Anangke and Tyke. What is man that he dare venture the fray? Each individual is scarcely more than a volume of quotations from the works of his ancestors, selected with little appropriateness to the Essay on Life which he has himself to compose. Mysterious and unrecorded influences extending over untold generations have combined to make him what he is, and to endow him with a personality which he can never escape from, nor transcend. The boy, the man, can no more run away from his parents than he can from himself. He may renounce and cast out the traits which he has inherited, but he cannot get rid of them. Unbidden and unnoticed, they will slink back and abide with him forever. They are not his servants, but belong to his family, his clan, his race. He can change or dismiss them no easier than he can the color of his skin or the shape of his skull. These are the laws of Heredity. They bind the individual as with a tether to an immovable stake. But the tether is not a fetter. It allows him a certain freedom, so that within the limits of those laws he can wonderfully modify himself and better his fortunes. More than that, he can “cozen the gods,” and outwit both Fate and Fortune, if he sets about it right. And how is that? By learning the laws of his own nature and of the physical surroundings which environ him. Knowing them, he can turn them to his own advantage.