The differentia of man--the quality that marks him off from the other animal kinds--is undoubtedly the power of articulate speech. Thereby his mind itself becomes articulate. If language is ultimately a creation of the intellect, yet hardly less fundamentally is the intellect a creation of language. As flesh depends on bone, so does the living tissue of our spiritual life depend on its supporting framework of steadfast verbal forms. The genius, the heaven-born benefactor of humanity, is essentially he who wrestles with "thoughts too deep for words," until at last he assimilates them to the scheme of meanings embodied in his mother-tongue, and thus raises them definitely above the threshold of the common consciousness, which is likewise the threshold of the common culture. There is good reason, then, for prefixing a short chapter on language to an account of those factors in the life of man that together stand on the whole for the principle of freedom--of rational self-direction. Heredity and environment do not, indeed, lie utterly beyond the range of our control. As they are viewed from the standpoint of human history as a whole, they show each in its own fashion a certain capacity to meet the needs and purposes of the life-force halfway. Regarded abstractly, however, they may conveniently be treated as purely passive and limiting conditions. Here we are with a constitution not of our choosing, and in a world not of our choosing. Given this inheritance, and this environment, how are we, by taking thought and taking risks, to achieve the best-under-the-circumstances? Such is the vital problem as it presents itself to any particular generation of men. The environment is as it were the enemy. We are out to conquer and enslave it. Our inheritance, on the other hand, is the impelling force we obey in setting forth to fight; it tingles in our blood, and nerves the muscles of our arm. This force of heredity, however, abstractly considered, is blind. Yet, corporately and individually, we fight with eyes that see. This supervening faculty, then, of utilizing the light of experience represents a third element in the situation; and, from the standpoint of man's desire to know himself, the supreme element. The environment, inasmuch as under this conception are included all other forms of life except man, can muster on its side a certain amount of intelligence of a low order. But man's prerogative is to dominate his world by the aid of intelligence of a high order. When he defied the ice-age by the use of fire, when he outfaced and outlived the mammoth and the cave bear, he was already the rational animal, _homo sapiens_. In his way he thought, even in those far-off days. And therefore we may assume, until direct evidence is forthcoming to the contrary, that he likewise had language of an articulate kind. He tried to make a speech, we may almost say, as soon as he had learned to stand up on his hind legs.