Note (return) — Chapter I

We generally think of 'instinct' as consisting of a number of such separate tendencies, each towards some distinct act or series of acts. But there is no reason to suppose that the whole body of inherited impulse even among non-human animals has ever been divisible in that way. The evolutionary history of impulse must have been very complicated. An impulse which survived because it produced one result may have persisted with modifications because it produced another result; and side by side with impulses towards specific acts we can detect in all animals vague and generalised tendencies, often overlapping and contradictory, like curiosity and shyness, sympathy and cruelty, imitation and restless activity. It is possible, therefore, to avoid the ingenious dilemma by which Mr. Balfour argues that we must either demonstrate that the desire, e.g. for scientific truth, is lineally descended from some one of the specific instincts which teach us 'to fight, to eat, and to bring up children,' or must admit the supernatural authority of the Shorter Catechism.[5]