According to The Quote Verifier (2006) by Ralph Keyes, Einstein never said any such thing. (According to p. 285 of the book's "source notes" Keyes checked New Statesman 16 April 1965, which is commonly cited as the source of this quote. Some other books claim it is from New Statesman 16 April 1955 and at least one has it as 1945, but a Google Books search http://books.google.com/advanced_book_search?num=10&q=einstein+watchmaker+%22new+statesman%22 with the date range restricted to 1900-1995 shows that all the earliest sources give it as 1965. This includes the earliest source located, The Penguin Dictionary of Modern Quotations from 1971, as can be verified by this search http://www.google.com/search?q=%22of+his+making+the+atom+bomb+possible.+quoted+in+new+statesman%2C+16+april+1965%22&btnG=Search+Books&tbm=bks&tbo=1.) Keyes notes that Einstein "did use similar words to make a very different point" when he wrote, in a 1954 letter to the editor at The Reporter magazine, "If I would be a young man again and had to decide how to make my living, I would not try to become a scientist or scholar or teacher. I would rather choose to be a plumber or a peddler in the hope to find that modest degree of independence still available under present circumstances."
Similarly, in Einstein and the Poet by William Hermanns, p. 86 http://books.google.com/books?id=QXCyjj6T5ZUC&lpg=PP1&pg=PA86#v=onepage&q&f=false, Einstein is quoted saying the following in a 1948 interview: "If I should be born again, I will become a cobbler and do my thinking in peace."
Misattributed
Variant: If only I had known, I should have become a watchmaker.
As quoted in Vietnam Past and Present: The North, ed. Andrew Forbes and David Henley (Cognoscenti Books, 2012)
From his memoirs: "Ontsporing" (English, "Derailment") Nov. 2012, page 175
“If I had known I was going to live this long, I'd have taken better care of myself!”
On one of his biggest regrets in "Julio Iglesias reflects on a life that 'has been a miracle'" https://apnews.com/7ef030336a5b4a1a949723346d64ec51 in AP News (2019 Jun 14)
“If we had known we were going to win control of the Senate, we'd have run better candidates.”
Attributed to Bob Dole by Charlie Cook, "The Democrats' Wild Ride," Cook Political Report, (June 12, 2010)
Letter to Pierre Chanut (Nov. 1, 1646) as quoted by Amir Aczel, Descartes' Secret Notebook (2005) citing René Descartes: Correspondance avec Elizabeth et autres lettres (1989) ed., Jean-Marie and M. Beysaade, pp. 245-246.
On being told his son had joined the Communist Party, as quoted in Try and Stop Me (1944) by Bennet Cerf
A statement similar in theme has also been attributed to Clemenceau:
A young man who isn't a socialist hasn't got a heart; an old man who is a socialist hasn't got a head.
As quoted in "Nice Guys Finish Seventh" : False Phrases, Spurious Sayings, and Familiar Misquotations (1992) by Ralph Keyes.
W. Gurney Benham in A Book of Quotations (1948) cites a statement by François Guizot as the earliest known expression of this general idea, stating that Clemenceau merely adapted the saying substituting socialiste for republicain:
N'être pas républicain à vingt ans est preuve d'un manque de cœur ; l'être après trente ans est preuve d'un manque de tête.
Not to be a republican at twenty is proof of want of heart; to be one at thirty is proof of want of head.
Variations on this general idea have also been attributed or misattributed to many others, most commonly Winston Churchill, who is not known to have actually made any similar statement.
Post-Prime Ministerial
As quoted in Freedomways, p. 232 (Second quarter, 1965).
in Karen Ilse Horn (ed.) Roads to Wisdom, Conversations With Ten Nobel Laureates in Economics (2009)
