Man's intelligence, it has so often been said, enables him to control Nature, but his intelligence in the control of natural resources is dependent for effectiveness on adequate material instruments. One may subscribe, though with qualification, to Bergson's further statement, that "intelligence, considered in what seems to be its original feature, is the faculty of manufacturing artificial objects, especially tools to make tools, and of indefinitely varying the manufacture." Anthropologists distinguish the prehistoric epochs, by such terms as the Stone, Copper or Bronze, and Iron Ages, meaning thereby to indicate what progress man had made in the utilization of the natural resources about him. We date the remote periods of mankind chiefly by the mementos we have of the kinds of tools they used and the methods they had developed in the control of their environment. The knowledge of how to start and maintain a fire has been set down as the practical beginning of civilization. Certainly next in importance was the invention of the simplest tools. There came in succession, though aeons apart, the use of chipped stone implements, bronze or copper instruments, and instruments made of iron. In the ancient world we find the invention of such simple machines as the pulley, the use of rope, and the inclined plane. Without tracing the history of invention, it will suffice for our purpose to point out that agriculture and industry, men's modes of exploiting Nature, are dependent intimately on the effectiveness of the tools at their disposal. It is a far cry from the flint hatchet to the McCormick reaper and the modern steel works, but these are two ends of the same process, that process which distinguishes man from all other animals, and makes human civilization possible: that is, the use and the manufacture of tools. CHAPTER II TYPES OF HUMAN BEHAVIOR AND THEIR SOCIAL SIGNIFICANCE--INSTINCT, HABIT, AND EMOTION INSTINCTIVE BEHAVIOR. We have already noted the fact that both men and animals are equipped with a wide variety of unlearned responses to given stimuli. In the case of human beings, this original equipment varies from such a specific reaction as pulling away the hand when it is pinched or burned, to such general innate tendencies as those of herding or playing with other people. In a later stage of this discussion we shall examine the more important of these primary modes of behavior. At this point our chief concern is with certain general considerations that apply to them all.