When we come to examine the laws of activity we find that, on the application of certain kinds of stimulus, there are certain very definite responses, and these we call instinctive. If the arm or the leg of a sleeper be stroked or touched, or a cold breath of air blows thereon, it will be withdrawn, and such withdrawal is what we call a reflex action. Now, an instinctive action, as Herbert Spencer saw long ago, is a "complex reflex action." It differs from a simple reflex, a mere twitch, such as winking, but it is a complicated, and possibly prolonged, action, which is, at bottom, of the nature of a reflex. One may instance the instinct of flight, which is correlated with fear. In crossing the street we hear "toot, toot," and we run. We do not ratiocinate, we run. All the primary instincts of mankind act similarly. Take, for contrast, the instinct of curiosity. Consider a child watching a mechanical toy; the impulse of this instinct of curiosity is such that he goes to the thing and examines it. By means of the transmutation, which it is the prerogative of man to effect, this instinct may work out into a lifetime devoted to the study of Nature. There is an unbroken sequence from the interest in the unknown which we see in a kitten or a child up to that which triumphs in a Newton or a Darwin. Thus we begin to learn that human nature is largely a collection of instincts, more or less correlated, and that at bottom we act on our instincts--in accordance with certain innate predilections, likings, and dislikings with which we were born, and which we have inherited from our ancestors. Indissolubly associated therewith is what we call emotion. For instance, in the exercise of the instinct of curiosity we feel a certain emotion, which we call wonder. There is an ignoble wonder and there is a noble wonder; but whether it be an astronomer watching the stars, or the crowd at a cinematograph show, there exists an association between the emotion of wonder and the instinct of curiosity. Dr. McDougall, of Oxford, elaborated some few years ago, and has now established, an extremely important theory of the relation between instinct and emotion. He has shown that our emotions are correlated with our instincts; that the emotion is the inward or subjective side of the working of the instinct. Thus an instinct is more than a "complex reflex action"; it is more than merely that, on hearing something, or seeing something, certain muscles are thrown into action, because along with the action there is emotion, and this is a natural and necessary correlation. We should do well to carry about with us, as part of our mental furniture, this idea of the correlation between instinct and emotion.