The scientist is accustomed to conquer truth only by degrees; for him all certainty should be bought by long hesitations, by perpetually feeling his way. He suspects what comes too easily, and accepts it only after submitting it to numerous and diverse proofs.
In: James Byrnie Shaw, Henri Poincare as an Investigator, The Popular Science Monthly, Volume 82, Number 3, March, 1913 (p. 211)