Not everything that can be extracted appears in anthologies of quotations, in commonplace books, or on the back of Celestial Seasonings boxes. Only certain sorts of extracts become quotations. – Gary Saul Morson, The Words of Others: From Quotations to Culture, 2011
I am now to offer some thoughts upon that sameness or familiarity which we frequently find between passages in different authors without quotation. This may be one of three things either what is called Plagiarism, or Imitation, or Coincidence. – James Boswell, “The Hypochondriack,” No.XXII, 1779

