To the superficial observer, a human being, during the interval between birth and adult life, seems to learn a great deal; but, if he did really learn all that he seems to learn, it would be marvelous in a degree wholly beyond the power of the human mind to conceive of, and far beyond the power of human language to express. Omitting, at present, that immense domain of the mind which is embraced under the terms sensation, emotion, and intellection, we will endeavor to make a comparative estimate as to how much we seem to learn, but do not learn, and how much we do really learn, in that limited department of the will which is covered by the term voluntary motion.
We will begin by endeavoring to ascertain how much a child would have to acquire in simply learning to pronounce the letter A, at will, supposing that none of the movements, or combinations of movements, which are made in the utterance of that one sound, are organic and inherited, but that they all have to be acquired or learned by practice and experience.
Between the states of the greatest and the least contraction of any muscle of the body, there are, of course, an infinite number of degrees of contraction. In order, however, that we may not seem to exaggerate the difficulties of the child's task, we will suppose that a muscle is susceptible of only three degrees of contraction, and that, therefore, three experiments, at most, would ultimate in the production of the sound of A, supposing it to depend upon the proper contraction of only one muscle. But how many muscles are engaged in the production of that one sound? A great many, namely, the muscles of the vocal chords, the muscles of the back part of the mouth, of the tongue, the cheeks, the lips, and the muscles that expand and contract the chest. We will largely understate their number, and suppose that there are only 20 involved in the pronunciation of A, each one of which, as we have already supposed, is susceptible of only 3 distinct degrees of contraction. Now, 2 muscles, each one of which is susceptible of 3 degrees of contraction, can be made to contract together in 9 different combinations, consisting of one degree of the contraction of each muscle to each combination; 3 muscles will give 27 possible combinations, 4 muscles 81 possible combinations, and so on, in a geometrical ratio of increase, up to the supposed 20 muscles, with which there would be 3,113,884,401 possible combinations of muscular contractions. Now, in all this wilderness of possibilities, there is but one combination which can produce the sound of the letter A, and that one the child must find, although, according to the supposition, he knows nothing about it, and has no organic tendencies in the direction toward it. He can find it only by experiment. Each possible combination must be successively tried and rejected, until he comes to the right one. Assuming that his chances of hitting upon the right combination are equal to his chances of missing it, the number of experiments which he would have to make,