“Within one cup pour vinegar and oil,
And look! unblent, unreconciled, they war.”

Source: Retaliation (1774), Line 11.

Vera; or, The Nihilists (1880)

Quote of Gainsborough in a 'Letter to Edward Stratford' (a patron), 1 May 1772
1770 - 1788

Source: The Souls of Black Folk (1903), Ch. I: Of Our Spiritual Strivings
Context: After the Egyptian and Indian, the Greek and Roman, the Teuton and Mongolian, the Negro is a sort of seventh son, born with a veil, and gifted with second-sight in this American world, — a world which yields him no true self-consciousness, but only lets him see himself through the revelation of the other world. It is a peculiar sensation, this double-consciousness, this sense of always looking at one's self through the eyes of others, of measuring one's soul by the tape of a world that looks on in amused contempt and pity. One ever feels his twoness, — an American, a Negro; two warring souls, two thoughts, two unreconciled strivings; two warring ideals in one dark body, whose dogged strength alone keeps it from being torn asunder.The history of the American Negro is the history of this strife, — this longing to attain self-conscious manhood, to merge his double self into a better and truer self.

Symposiacs, book viii. Question IX
Bartlett's Familiar Quotations, 10th ed. (1919)

Section 1 “Marque and Reprisal”, Chapter V (pp. 37-38)
The Star Fox (1965)

Source: Rigante series, Stormrider, Ch. 7
Context: No need for confusion, my dear Mulgrave [... ] Beautiful wine and sour vinegar come from exactly the same source. Curiously if one leaves a bottle of wine open for long enough it will become vinegar. Happily in this house wine never survives long enough to go bad.

Song lyrics, The Dreaming (1982)

"The Neighbors"
Actor (2009)