'When one is learning a language, he attends to the sounds, but when he is master of it, he attends only to the sense of what he would express. If this is the case, we must become as little children again, if we will be philosophers: we must overcome habits which have been gathering strength ever since we began to think; habits, the usefulness of which atones for the difficulty it creates for the philosopher in discovering the first principles of the human mind.'