Some who have never raised their minds to the consideration of the real
dignity of the art, and who rate the works of an artist in proportion as
they excel, or are defective in the mechanical parts, look on theory as
something that may enable them to talk but not to paint better, and
confining themselves entirely to mechanical practice, very assiduously
toil on in the drudgery of copying, and think they make a rapid progress
while they faithfully exhibit the minutest part of a favourite picture.
This appears to me a very tedious, and I think a very erroneous, method
of proceeding. Of every large composition, even of those which are most
admired, a great part may be truly said to be common-place. This, though
it takes up much time in copying, conduces little to improvement. I
consider general copying as a delusive kind of industry; the student
satisfies himself with the appearance of doing something; he falls into
the dangerous habit of imitating without selecting, and of labouring
without any determinate object; as it requires no effort of the mind, he
sleeps over his work; and those powers of invention and composition which
ought particularly to be called out and put in action lie torpid, and
lose their energy for want of exercise.

It is an observation that all must have made, how incapable those are of
producing anything of their own who have spent much of their time in
making finished copies.

To suppose that the complication of powers, and variety of ideas
necessary to that mind which aspires to the first honours ill the art of
painting, can be obtained by the frigid contemplation of a few single
models, is no less absurd than it would be in him who wishes to be a poet
to imagine that by translating a tragedy he can acquire to himself
sufficient knowledge of the appearances of nature, the operations of the
passions, and the incidents of life.