“I think that only daring speculation can lead us further and not accumulation of facts.”
Letter to Michele Besso (8 October 1952). According to Scientifically speaking: a dictionary of quotations, Volume 1 (2002), p. 154 http://books.google.com/books?id=FFIBzawsfPEC&lpg=PR1&pg=PA154#v=onepage&q&f=false, the letter is reprinted on p. 487 of Correspondance 1903-1955 (1972) by Michele Besso.
1950s
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Albert Einstein 702
German-born physicist and founder of the theory of relativi… 1879–1955Related quotes

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“Only those who have dared to let go can dare to reenter.”
Quoted in Geary's Guide to the World's Great Aphorists (2007) by James Geary, p. 232

“Dare to be free, dare to go as far as your thought leads, and dare to carry that out in your life.”

When asked to estimate the number of casualties terrorist attacks at the World Trade Center, at a news conference (11 September 2001) http://transcripts.cnn.com/TRANSCRIPTS/0109/11/bn.42.html; this is often misquoted as "More than we can bear."