The inconsistency between the rational professions and the impulsive behavior of men is a matter of common observation. "That's not the logic, reason, or philosophy of it, but it's the human nature of it." It is now generally recognized that the older English conception of the "economic man" and the "rational man," motivated by enlightened self-interest, was far removed from the "natural man" impelled by impulse, prejudice, and sentiment, in short, by human nature. Popular criticism has been frequently directed against the reformer in politics, the efficiency expert in industry, the formalist in religion and morals on the ground that they overlook or neglect the so-called "human factor" in the situation. Sir Arthur Helps says: No doubt hard work is a great police-agent; if everybody were worked from morning till night, and then carefully locked up, the register of crimes might be greatly diminished. But what would become of human nature? Where would be the room for growth in such a system of things? It is through sorrow and mirth, plenty and need, a variety of passions, circumstances, and temptations, even through sin and misery, that men's natures are developed. Certain sayings already quoted imply that the nature of man is a fact to be reckoned with in controlling his behavior. "There are limits to human nature" which cannot lightly be overstepped. "Human nature," according to Periander, "is hard to overcome." Yet we also recognize with Swift that "it is the talent of human nature to run from one extreme to another." Finally, nothing is more trite and familiar than the statement that "human nature is the same all over the world." This fundamental likeness of human nature, despite artificial and superficial cultural differences, has found a classic expression in Kipling's line: "The Colonel's Lady an' Judy O'Grady are sisters under their skins!" Human nature, then, as distinct from the formal wishes of the individual and the conventional order of society, is an aspect of human life that must be reckoned with. Common sense has long recognized this, but until recently no systematic attempt has been made to _isolate_, describe, and explain the distinctively human factors in the life either of the individual or of society. Of all that has been written on this subject the most adequate statement is that of Cooley. He has worked out with unusual penetration and peculiar insight an interpretation of human nature as a product of group life. By human nature we may understand those sentiments and impulses that are human in being superior to those of lower animals, and also in the sense that they belong to mankind at large, and not to any particular race or time. It means, particularly, sympathy and the innumerable sentiments into which sympathy enters, such as love, resentment, ambition, vanity, hero-worship, and the feeling of social right and wrong.