When we recognize that decisions due to instinct come into the mind in a form so characteristic and easily identifiable we are encouraged at once to ask {16} whether all decisions having this form must be looked upon as essentially of instinctive origin. Inquiry, however, reveals the fact that the bulk of opinion based upon assumptions having these introspectual characters is so vast that any answer but a negative one would seem totally incompatible with current conceptions of the nature of human thought.2
Many attempts have been made to explain the behaviour of man as dictated by instinct. He is, in fact, moved by the promptings of such obvious instincts as self-preservation, nutrition, and sex enough to render the enterprise hopeful and its early spoils enticing. So much can so easily be generalized under these three impulses that the temptation to declare that all human behaviour could be resumed under them was irresistible. These early triumphs of materialism soon, however, began to be troubled by doubt. Man, in spite of his obvious duty to the contrary, would continue so often not to preserve himself, not to