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."<br>Other variants: <br class="br">The eternally incomprehensible thing about the world is its comprehensibility. <br class="br">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. <br class="br">The most incomprehensible thing about the world is that it is comprehensible. <br class="br">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. <br class="br">The most incomprehensible thing about the world is that it is at all comprehensible. <br class="br">As quoted in Speaking of Science (2000) by Michael Fripp <br class="br">The eternal mystery of the world is its comprehensibility … The fact that it is comprehensible is a miracle. <br class="br">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. <br class="br">1930s