The test of intelligence is the power to act successfully in new situations. We judge a man to be intelligent when we see that in going through the world he is not guided merely by routine or second-hand ideas, but that when he meets a fresh difficulty he thinks out a fresh line of action appropriate to it, which is justified by its success. We value the faculty because it does succeed, because in the changing world of human life we feel a constant need for it. In animal existence, where situations repeat themselves day after day, and generation after generation, with practical uniformity, a successful method of behavior may be worked out by unintelligent adaptation, and may become fixed in instinct or habit, but the power to deal effectively with intricate and shifting forces belongs to intelligence alone. It is, then, essentially a kind of foresight, a mental reaction that anticipates the operation of the forces at work and is prepared in advance to adjust itself to them. How is this possible when the situation is a new one whose working cannot have been observed in the past? The answer is that the situation is new only as a whole, and that it always has elements whose operation is familiar. Intelligence is the power to anticipate how these elements will work in a novel combination: it is a power of grasp, of synthesis, of constructive vision.[75] It does not dispense with experience. A man who can take hold of a new undertaking and make it go will commonly be a man who has prepared himself by previous undertakings of a similar character: the more pertinent experience he has had the better. If he is opening a business agency in a strange city he will require a general acquaintance with the business, such as he might gain at the home office, and will do well also to learn all he can in advance about the city into which he goes. But beyond this he will need the power to take a fresh, understanding view of the situation as he actually finds it, the state of the market, the people with whom he deals and the like, so as to perceive their probable working in relation to his own designs. Intelligence, then, is based on memories, but makes a free and constructive use of these, as distinguished from a mechanical use. By an act of mental synthesis it grasps the new combination as a going whole and foresees how it must work. It apprehends life through an inner organizing process of its own, corresponding to the outward process which it needs to interpret, but working in advance of the latter and anticipating the outcome.