Quotes from Mikhail Leonidovich Gromov

But anything that can be called "rigor" is lost exactly where the things become interesting and non trivial.

But 'the physical level of rigor' is higher on certainty than the logical one, since reproducible experiments are more reliable than anybody's, be it Hilbert's, Einstein's or Gödel's intuition.

Understanding what and why did not work may be more instructive than celebrating our successes.