Alexander Pope, An Essay on Criticism, second edition, Part 2, lines 256-269:1

Whoever thinks a faultless Piece to see,
  Thinks what ne’er was, nor is, nor e’er shall be.
In ev’ry Work regard the Writer’s End,
  Since none can compass more than they Intend;
  And if the Means be just, the Conduct true,
  Applause, in spite of trivial Faults, is due.
As Men of Breeding, oft the Men of Wit
  T’ avoid great Errors, must the less commit,
  Neglect the Rules each Verbal Critick lays,
  For not to know some Trifles, is a Praise.
Most Criticks fond of some subservient Art,
  Still make the Whole depend upon a Part,
  They talk of Principles, but Parts they prize,
  And All to one lov’d Folly Sacrifice.