From twelve to fifteen, Emile’s education is equally practical. Curiosity moves him to experiment and discovery, and thus he learns the simple truths of science without teaching. Locke’s belief in utility was not greater than Rousseau’s. The word “useful”, he says, is the key to the whole situation. Emile is always to test his discoveries by the question “What is this good for?” and things which do not satisfy this test are of no account. The tutor still attends the boy like his shadow, never seeming to influence the course of events; but since Nature cannot be trusted to adapt herself to his scheme, he now finds it necessary to contrive artificial experiences which Emile accepts as natural.