your own industry; but the industry which I principally recommended, is
not the industry of the _hands_, but of the _mind_.

As our art is not a divine gift, so neither is it a mechanical trade. Its
foundations are laid in solid science. And practice, though essential to
perfection, can never attain that to which it aims, unless it works under
the direction of principle.

Some writers upon art carry this point too far, and suppose that such a
body of universal and profound learning is requisite, that the very
enumeration of its kind is enough to frighten a beginner. Vitruvius,
after going through the many accomplishments of nature, and the many
acquirements of learning, necessary to an architect, proceeds with great
gravity to assert that he ought to be well skilled in the civil law, that
he may not be cheated in the title of the ground he builds on.

But without such exaggeration, we may go so far as to assert, that a
painter stands in need of more knowledge than is to be picked off his
pallet, or collected by looking on his model, whether it be in life or in
picture. He can never be a great artist who is grossly illiterate.

Every man whose business is description ought to be tolerably conversant
with the poets in some language or other, that he may imbibe a poetical
spirit and enlarge his stock of ideas. He ought to acquire a habit of
comparing and divesting his notions. He ought not to be wholly
unacquainted with that part of philosophy which gives him an insight into
human nature, and relates to the manners, characters, passions, and
affections. He ought to know something concerning the mind, as well as a
great deal concerning the body of man.