That part of a work of one author found in another is not of itself piracy, or sufficient to support an action; a man may adopt part of the work of another; he may so make use of another’s labors for the promotion of science and the benefit of the public. – Lord Ellenborough, quoted in Bouvier’s Law Dictionary by John Bouvier, 8th

When a man thinks happily, he finds no foot-track in the field he traverses. All spontaneous thought is irrespective of all else. – Ralph Waldo Emerson, “Quotation and Originality,” Letters and Social Aims, 1876

When a thing has been said and well said, have no scruple: take it and copy it. – Anatole France, “The Creed”

But further, in order to embellish it with flowers of language and gems of thought, it is not necessary for this ornamentation to be spread evenly over the entire speech, but it must be so distributed that there may be brilliant jewels placed at various points as a sort of decoration. – Cicero, De oratore