according to rules; and they do not differ specifically from what can be acquired by industry through imitation. Thus we can readily learn all that Newton has set forth in his immortal work on the Principles of Natural Philosophy, however great a head was required to discover it; but we cannot learn to write spirited poetry, however express may be the precepts of the art and however excellent its models. The reason is that Newton could make all his steps, from the first elements of geometry to his own great and profound discoveries, intuitively plain and definite as regards consequence, not only to himself but to everyone else. But a Homer or a Wieland cannot show how his Ideas, so rich in fancy and yet so full of thought, come together in his head, simply because he does not know and therefore cannot teach others.