Most of the classical citations you shall hear or read in the current journals or speeches were not drawn from the originals, but from previous quotations in English books… – Ralph Waldo Emerson, “Quotation and Originality,” Letters and Social Aims, 1876

Mr. [Thomas] Gray the poet has often observed to me that if a man were to form a Book of what he had seen and heard himself it must in whatever hands prove a most useful and entertaining one. – Horace Walpole, quoted in Walpoliana, 1800

Do not shun this maxim because it is common-place. On the contrary, take the closest heed of what observant men, who would probably like to show originality, are yet constrained to repeat. Therein lies the marrow of the wisdom of the world. – Arthur Helps, “Chapter IV,” Companions of My Solitude, 1851

Reframing an extract as a quotation constitutes a kind of coauthorship. With no change in wording, the cited passage becomes different. I imagine that the thrill of making an anthology includes the opportunity to become such a coauthor. – Gary Saul Morson, The Words of Others: From Quotations to Culture, 2011