“you must see that if two things are alike, then it is a further question whether the first is copied from the second, or the second from the first, or both from a third.’ ‘Some that thought that all these loves were copies of our love for the landlord.”

From Rudyard Kipling, The Ballad of the King's Jest; quoted in the opening of Rival Caesars
Misattributed

Lives of Wives (London: Cassell, 1939)

Variant: if you love two people at the same time, choose the second. Because if you really loved the first one, you wouldn't have fallen for the second.

Appendix, The relations of Logarithms & their natural numbers to each other
The Construction of the Wonderful Canon of Logarithms (1889)

Summations, Chapter 58

Source: Twisted

Introductio ad prudentiam: Part II (1727), Gnomologia (1732)

The Architecture of Theories (1891)
Context: The origin of things, considered not as leading to anything, but in itself, contains the idea of First, the end of things that of Second, the process mediating between them that of Third. A philosophy which emphasises the idea of the One, is generally a dualistic philosophy in which the conception of Second receives exaggerated attention: for this One (though of course involving the idea of First) is always the other of a manifold which is not one. The idea of the Many, because variety is arbitrariness and arbitrariness is repudiation of any Secondness, has for its principal component the conception of First. In psychology Feeling is First, Sense of reaction Second, General conception Third, or mediation. In biology, the idea of arbitrary sporting is First, heredity is Second, the process whereby the accidental characters become fixed is Third. Chance is First, Law is Second, the tendency to take habits is Third. Mind is First, Matter is Second, Evolution is Third.

On his stated opposition to the use of the atomic bomb against the Japanese at the end of World War II, as quoted in Newsweek (11 November 1963), p. 107
1960s