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

We prefer to think that the absence of inverted commas guarantees the originality of a thought, whereas it may be merely that the utterer has forgotten its source. – Clifton Fadiman, The American Treasury, 1455-1955, 1955

Dr. Richard Bentley (1662-1742)… is said one day, on finding his son reading a novel, to have remarked—’Why read a book that you cannot quote?’— a saying which affords an amusing illustration of the nature and object of his literary studies. – Cyclopædia of English Literature edited by Robert Chambers, 1844