Let us study this phenomenon of instinct. A child begins to play on the piano. At first she must pay attention to every key she is fingering, and as she goes on and on for months and years, the playing becomes almost involuntary, instinctive. What was first done with conscious will does not require later on an effort of the will. This is not yet a complete proof. One half remains, and that is that almost all the actions which are now instinctive can be brought under the control of the will. Each muscle of the body can be brought under control. This is perfectly well known. So the proof is complete by this double method, that what we now call instinct is degeneration of voluntary actions; therefore, if the analogy applies to the whole of creation, if all nature is uniform, then what is instinct in lower animals, as well as in men, must be the degeneration of will.