From Christian Felix Klein´s “Lectures on mathematics in the 19th century”:
The secret of brilliant productivity will always be discovering new problems and intuiting new theorems, which open the way to new results and connections. Without the creation of new viewpoints, without positing new aims, mathematics would soon exhaust itself in the rigor of logical proofs and begin to stagnate, as it would run out of content. In a way, mathematics has been best served by those who distinguished themselves more by intuitions than by rigorous proofs.
(Taken from Edmund Phelps´ “Mass Flourishing” (page 19))
(Christian Felix Klein (25 April 1849 – 22 June 1925) was a German mathematician, known for his work in group theory, complex analysis, non-Euclidean geometry, and on the connections between geometry and group theory. His 1872 Erlangen Program, classifying geometries by their underlying symmetry groups, was a hugely influential synthesis of much of the mathematics of the day.)