III YET what we consider our highest activities arise out of what we are accustomed to regard as the lowest. That is, indeed, merely a necessary result of evolution; bipeds like ourselves spring out of many-limbed creatures whom we should now regard as little better than vermin, and the adult human creature whose eyes, as he sometimes imagines, are fixed on the stars, was a few years earlier merely a small animal crawling on all fours. The impulse of the philosopher, of the man of science, of any ordinary person who sometimes thinks about seemingly abstract or disinterested questions—we must include the whole range of the play of thought in response to the stimulus of curiosity—may seem at the first glance to be a quite secondary and remote product of the great primary instincts. Yet it is not difficult to bring this secondary impulse into direct relation with the fundamental primary instincts, even, and perhaps indeed chiefly, with the instinct of sex. On the mental side—which is not, of course, its fundamental side—the sexual instinct is mainly, perhaps solely, a reaction to the stimulus of curiosity. Beneath that mental surface the really active force is a physiologically based instinct urgent towards action, but the boy or girl who first becomes conscious of the mental stimulus is unaware of the instinct it springs from, and may even disregard as unimportant its specific physiological manifestations. The child is only conscious of new curiosities, and these it persistently seeks to satisfy at any available or likely source of information, aided by the strenuous efforts of its own restlessly active imagination. It is in exactly the same position as the metaphysician, or the biologist, or any thinker who is faced by complex and yet unsolved problems. And the child is at first baffled by just the same kind of obstacles, due, not like those of the thinker, to the silence of recalcitrant Nature, but to the silence of parents and teachers, or to their deliberate efforts to lead him astray. Where do babies come from? That is perhaps for many children the earliest scientific problem that is in this way rendered so difficult of solution. No satisfying solution comes from the sources of information to which the child is wont to appeal. He is left to such slight imperfect observations as he can himself make; on such clues his searching intellect works and with the aid of imagination weaves a theory, more or less remote from the truth, which may possibly explain the phenomena. It is a genuine scientific process—the play of intellect and imagination around a few fragments of observed fact—and it is undoubtedly a valuable discipline for the childish mind, though if it is too prolonged it may impede or distort natural development, and if the resulting theory is radically false it may lead, as the theories of scientific adults sometimes lead, if not speedily corrected, to various unfortunate results.