Besides it is an error to believe that rigour is the enemy of simplicity. On the contrary we find it confirmed by numerous examples that the rigorous method is at the same time the simpler and the more easily comprehended. The very effort for rigor forces us to find out simpler methods of proof.
David HilbertHe who seeks for methods without having a definite problem in mind seeks in the most part in vain.
David HilbertOne can measure the importance of a scientific work by the number of earlier publications rendered superfluous by it
David Hilbert