6. Hence, if wealth comprises all valuable objects, and if every desirable object which involves sacrifice has value, it would be a proper definition to say that _wealth consists of all those objects and qualities useful to man, the attainment of which involves sacrifice_. This includes not only material objects and qualities, but also all those human powers acquired by sacrifice, which enable man to master nature. This is not admitted by many writers. But Mr. Carey states, in a broad way, that “Wealth is the power to command the always gratuitous services of nature.” When man is at his weakest nature does nothing for him. Every infant, if dependent on nature alone, would inevitably perish. So in the infancy of society, it is only by the most strenuous exertion that a precarious existence is secured. But with every increment of power in man, nature multiplies her services. They are not bought but freely given, and given as soon as man is able to command them. In the most advanced civilization the forces of nature have become so subservient to man that in thousands of cases one can accomplish what a score, or sometimes even a hundred, could not formerly have done. It is this increase of power more than that of material commodities which constitutes the real wealth of the world. 7. From this it follows that the proper subject of political economy is MAN. The laws pertaining to the underlying science are found in the nature and character of man—in his tastes, his desires, in the motives influencing him and in the limitations to which he is subject. The results to be achieved are his prosperity and freedom, his mastery over nature, and his happiness. Here, then, is the prime reason why every person who aspires to any intelligence at all should have some acquaintance with this subject. It has to do more than any other study with his temporal welfare, and with the welfare of society, without the prosperity of which his individual prosperity will suffer. 8. A second reason is implied in the meaning of the terms used. Economy is from a Greek compound signifying _husbandry_. It has reference to the prudent management by a householder of his means so as to secure the largest measure of prosperity for his family. It does not mean parsimony, nor even mere frugality; that is, it does not consist in mere abstinence for the sake of saving. It is rather a wise use of means and forces, so as to make them as effective as possible. There is an old proverb which says, “There is more in calculation than in hard work,” and though sometimes perverted in the interest of human laziness, it is nevertheless full of philosophy. It is this “calculation” which such a study greatly aids.