Thanks to the piling up of reserves of energy, which is a result of inhibition, the organism can carry out its work of differentiation, can develop organs and organic systems, and obtain the power to perform more complicated functions; these render it ever more independent of the outer world and enable it to affect the outer world to an increasing extent. Inhibition plays an important part in differentiation. Its apparatus becomes organized. The nerve centres from which the inhibition proceeds form a ladder of which each rung is subordinate to the next. The peripheral nerves are controlled by the nerve centres in the spinal cord, these again by the centres in the medulla oblongata, and then in succession by the cerebellum and the cerebrum, and finally by the corticle. On the principle of least resistance, on which all life is based, the highest centres of inhibition unburden themselves by granting the lower ones a certain measure of independence. The reaction to the most ordinary and frequent stimuli is controlled and organized in its character and strength by the apparatus of inhibition, so that it ensues automatically, and no active inhibition, that is, no conscious effort of the will, is required. The simplest of these automatic reflex movements take place below the level of consciousness.
Those organized complexes of movement, however, which we call instincts, are carefully watched by the consciousness and subjected to severe check if they appear to run counter to the supposed interest of the organism. The hereditary complexes of movement constituting instinct are highly organized and oppose inhibition, only yielding to it when it is stronger than they are. This can be observed in animals which are capable of taming and training. All the artificial actions and omissions that man teaches them are triumphs of inhibition over automatism. Among human beings it is only the elect who can vigorously suppress their instincts by inhibition directed by Reason. The being that has attained the summit of organic evolution on earth is man, in whom only the lower, vegetative life processes are liable to the influence of tropism and primary reflex actions, while all the higher and highest functions are the work of Reason, which arms the will with inhibition and suppresses all impulses and actions that hinder its purposes. It is characteristic of these functions that they are first worked out as concepts by the consciousness before they are realized as movements.