The arts would lie open for ever to caprice and casualty, if those who
are to judge of their excellences had no settled principles by which they
are to regulate their decisions, and the merit or defect of performances
were to be determined by unguided fancy. And indeed we may venture to
assert that whatever speculative knowledge is necessary to the artist, is
equally and indispensably necessary to the connoisseur.

The first idea that occurs in the consideration of what is fixed in art,
or in taste, is that presiding principle of which I have so frequently
spoken in former discourses, the general idea of nature. The beginning,
the middle, and the end of everything that is valuable in taste, is
comprised in the knowledge of what is truly nature; for whatever ideas
are not conformable to those of nature, or universal opinion, must be
considered as more or less capricious.

The idea of nature comprehending not only the forms which nature
produces, but also the nature and internal fabric and organisation, as I
may call it, of the human mind and imagination: general ideas, beauty, or
nature, are but different ways of expressing the same thing, whether we
apply these terms to statues, poetry, or picture. Deformity is not
nature, but an accidental deviation from her accustomed practice. This
general idea therefore ought to be called nature, and nothing else,
correctly speaking, has a right to that name. But we are so far from
speaking, in common conversation, with any such accuracy, that, on the
contrary, when we criticise Rembrandt and other Dutch painters, who
introduced into their historical pictures exact representations of
individual objects with all their imperfections, we say, though it is not
in a good taste, yet it is nature.