We must, then, have clear in our minds the idea that everything that happens to a child and that may produce a reaction or an effect is worth considering from the point of view of its influence upon his development. Indeed, instead of discussing heredity _versus_ environment, we should try to conceive of the personality of the child as made up of the effect of a certain heredity responding to a certain environment. For example, the child inherits the instinct to handle things. At a certain age this instinct will take the form of handling objects within reach, and of breaking them. We cannot say that the child has an instinct for breaking vases or tearing books; he has simply the instinct to _do_ something with material that he can handle. Now, it is possible for the child to exercise this instinct only on material that can be broken or torn; it is also possible for the child to exercise it on material that can be manipulated constructively--as blocks for building, clay for shaping, or, later, tools of various kinds. In one case the child establishes habits of tearing or breaking; in the other the same instincts--the same "heredity," that is--issues in habits of _making_. Or we may take the instinct of curiosity, which every normal child will manifest at an early stage. This instinct may find exercise in wondering what is in parcels or closed cupboards; or it may exercise itself in wondering about the thunder and the flowers and the things under the earth; or it may be quite suppressed by discouragement or by unsatisfying indulgence. Thus the same instinct may lead under different treatments to different results. This does not mean that every child has the making of an investigator; it means that a perfectly healthy instinct capable of being turned to good use is often perverted or crushed out because we have not learned to cultivate it profitably through control of the growing child's development.