“Married people pledge love for each other throughout eternity. Well, now, that is easy enough but does not mean very much, for if one is finished with time one is probably finished with eternity. If, instead of saying "throughout eternity," the couple would say, "until Easter, until next May Day," then what they say would make some sense, for then they would be saying something and also something they perhaps could carry out.”
Hong, 1987/2013. p. 296
1840s, Either/Or (1843)
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Sören Kierkegaard 309
Danish philosopher and theologian, founder of Existentialism 1813–1855Related quotes

“One may say "the eternal mystery of the world is its comprehensibility."”
From the article "Physics and Reality" (March 1936), reprinted in Out of My Later Years (1956). The quotation marks may just indicate that he wants to present this as a new aphorism, but it could possibly indicate that he is paraphrasing or quoting someone else — perhaps Immanuel Kant, since in the next sentence he says "It is one of the great realizations of Immanuel Kant that the setting up of a real external world would be senseless without this comprehensibility."
Other variants:
The eternally incomprehensible thing about the world is its comprehensibility.
In the endnotes to Einstein: His Life and Universe by Walter Isaacson, note 46 on p. 628 http://books.google.com/books?id=cdxWNE7NY6QC&lpg=PP1&pg=PA628#v=onepage&q&f=false says that "Gerald Holton says that this is more properly translated" as the variant above, citing Holton's essay "What Precisely is Thinking?" on p. 161 of Einstein: A Centenary Volume edited by Anthony Philip French.
The most incomprehensible thing about the world is that it is comprehensible.
This version was given in Einstein: A Biography (1954) by Antonina Vallentin, p. 24, and widely quoted afterwards. Vallentin cites "Physics and Reality" in Journal of the Franklin Institute (March 1936), and is possibly giving a variant translation as with Holton.
The most incomprehensible thing about the world is that it is at all comprehensible.
As quoted in Speaking of Science (2000) by Michael Fripp
The eternal mystery of the world is its comprehensibility … The fact that it is comprehensible is a miracle.
As quoted in Einstein: His Life and Universe by Walter Isaacson, p. 462 http://books.google.com/books?id=cdxWNE7NY6QC&lpg=PP1&pg=PA462#v=onepage&q&f=false. In the original essay "The fact that it is comprehensible is a miracle" appears at the end of the paragraph that follows the paragraph in which "The eternal mystery of the world is its comprehensibility" appears.
1930s

Quote from an interview, 1966; as quoted in Minimal Art, a Critical Anthology, ed. Gregory Battcock, University of California Press, Berkeley 1968, p. 157-161
Quotes, 1960 - 1970

translation from original Dutch, Fons Heijnsbroek, 2018
version in original Dutch / citaat van Jacob Maris, in het Nederlands: Daarentegen wordt mij verweten dat mijn schilderijen niet af zijn, hoe ik mijn lucht ook doorwerkt heb. Nu, 'af' in de gewone beteekenis van het woord is mijn werk zeker niet. Door in dien zin het af te maken, zou ik er het leven uithalen.
in Jacob Maris (1837-1899), M. van Heteren and others; as cited in 'Ik denk in mijn materie', in exhibition catalog of Teylers Museum / Museum Jan Cunen), Zwolle 2003, p. 76

“Hauling fish from the sea—what endless toil. One could almost say, what an eternal problem.”
Heimsljós (World Light) (1940), Book Three: The House of the Poet

“Eternal vigilance. Remember, no one said democracy would be easy.”
Source: Authoritarian Nightmare (2020), p. 282

“You say that in heaven there is eternal beauty. The eternal beauty is here and now, not in heaven.”
When the Shoe Fits

Cassandra (1860)

Letter to A.S. Suvorin (December 9, 1890)
Letters