Since any faculty grows by its own exercise, just as muscles grow by exercise, every time the baby succeeds in getting his hands to his mouth as a result of desire, every time that he succeeds in grasping an object as result of desire, his will power grows. Action of this nature brings in new sensations, and the brain centers used for recording such sensations grow. As the sensations multiply, he compares them, and an idea is born. For the beginnings of mental development no other mechanism is actually needed than a brain and a hand and the nerves connecting them. Laura Bridgeman and Helen Keller, both of them deaf and blind, received their education almost entirely through their hands, and yet they were unusually capable of thinking. The child's hands, then, from the beginning, are the servants of his brain-instruments by means of which he carries impressions from the outer world to the seat of consciousness, and by which in turn he imprints his consciousness upon the outer world. [Sidenote: Intentional Grasping] The average baby does not begin to grasp objects with intention before the fourth month. The first grasping seems to be done by feeling, without the aid of the eye, and is done with the fingers with no attempt to oppose the thumb to them. So closely does the use of the thumbs set opposite the fingers in grasping coincide with the first grasping with the aid of sight, that some observers have been led to believe that as soon as the baby learns to use its thumb in this way he proves that he is beginning to grasp with intention. [Sidenote: Order of Development] The order of development seems to be, _first_, automatism, the muscles contracting of themselves in response to nervous stimuli; _second_, instinct, the inherited wisdom of the race, which discovered ages ago that the hand could be used to greater advantage when the thumb was separated from the fingers; and _thirdly_, the child's own intelligence and will making use of this natural and inherited machinery. This order holds true of the development, not only of the hand, but of the whole organism. [Sidenote: Looking] A little earlier than this, during the third month, the baby first looks upon his own hands and notices them. Darwin tells us that his boy looked at his own hands and seemed to study them until his eyes crossed. About the same then the child notices his foot and uses his hand to carry it to its mouth. It is some time later that he discovers that he can move his feet without his hands. [Sidenote: Tearing]