himself to an environment of vastly greater complexity. By means of written symbols, representing words or thoughts, he is not only able to store in a form easily available to himself, his fellows, and his descendants accumulations of knowledge so immense that no memory could contain them, but by means of these symbols he is able (e.g. in the mathematics) to perform feats of thinking utterly beyond the powers of the unaided mind; just as by means of tools, machinery, and other mechanical contrivances he is able to perform physical feats utterly beyond the unaided powers of his body. To written symbols representing words or thoughts is due, practically speaking, his whole advance beyond the savage in the past, and to them are due also his vast potentialities for future advance.
