“Be crazy! But learn how to be crazy without being the center of attention. Be brave enough to live different.”

Said to Wolfgang Pauli after his presentation of Heisenberg's and Pauli's nonlinear field theory of elementary particles, at Columbia University (1958), as reported by F. J. Dyson in his paper “Innovation in Physics” (Scientific American, 199, No. 3, September 1958, pp. 74-82; reprinted in "JingShin Theoretical Physics Symposium in Honor of Professor Ta-You Wu," edited by Jong-Ping Hsu & Leonardo Hsu, Singapore; River Edge, NJ: World Scientific, 1998, pp. 73-90, here: p. 84).
Your theory is crazy, but it's not crazy enough to be true.
As quoted in First Philosophy: The Theory of Everything (2007) by Spencer Scoular, p. 89
There are many slight variants on this remark:
We are all agreed that your theory is crazy. The question which divides us is whether it is crazy enough.
We are all agreed that your theory is crazy. The question is whether it is crazy enough to be have a chance of being correct.
We in the back are convinced your theory is crazy. But what divides us is whether it is crazy enough.
Your theory is crazy, the question is whether it's crazy enough to be true.
Yes, I think that your theory is crazy. Sadly, it's not crazy enough to be believed.

Original: Rivoluzionate voi stessi: siate leali, folli, gentili e coraggiosi... siate migliori.
Source: prevale.net

Source: 2000s and posthumous publications, A Time Odyssey, Sunstorm (2005), Chapter 27, “The Tin Lid” (p. 207)

Source: Briar Rose (1992), Chapter 24 (p. 131)

Interview http://www.youtube.com/watch?v=6C6K0umwZwo by Diane Sawyer (1994)

VALIS

Source: Burning Paradise (2013), Chapter 22 (p. 222)