"We learn to talk, much about the same time that we learn to walk, but talking requires less muscular effort than walking, and makes generally less demand upon our powers. A man may talk a long while before he has done the equivalent of a five-mile walk; it is natural, therefore, that we should have had more practice in talking than in walking, and hence that we should find it harder to pay attention to our words than to our steps. Certainly it is ver y hard to become conscious of every syllable ...