“The scientist has marched in and taken the place of the poet. But one day somebody will find the solution to the problems of the world and remember, it will be a poet, not a scientist.”

"The Reach of Imagination" (1967)

Source: Letters to a Young Scientist (2013), chapter 5, "The Creative Process", page 74.

Partly cited in: Jean-Marc Choukroun, Roberta Snow (1992) Planning for human systems: essays in honor of Russell L. Ackoff. p. 287.
1950s, The development of operations research as a science, 1956

"The Man Who Named the World" (1990)

Statement upon being appointed as UC Berkeley chancellor in 1958, as quoted Biographical Memoirs (2000) edited by Darleane C. Hoffman, p, 252 <!-- ISBN 0-309-07035-X National Academies Press-->
Context: There is a beauty in discovery. There is mathematics in music, a kinship of science and poetry in the description of nature, and exquisite form in a molecule. Attempts to place different disciplines in different camps are revealed as artificial in the face of the unity of knowledge. All literate men are sustained by the philosopher, the historian, the political analyst, the economist, the scientist, the poet, the artisan and the musician.

"Mammon" an address at the London School of Economics (6 December 1963); published in Mammon and the Black Goddess (1965).
General sources

Mathematical Methods in Science (1977)
Context: We wish to see... the typical attitude of the scientist who uses mathematics to understand the world around us.... In the solution of a problem... there are typically three phases. The first phase is entirely or almost entirely a matter of physics; the third, a matter of mathematics; and the intermediate phase, a transition from physics to mathematics. The first phase is the formulation of the physical hypothesis or conjecture; the second, its translation into equations; the third, the solution of the equations. Each phase calls for a different kind of work and demands a different attitude.<!--p.164