“War itself is not a mere science but a more fickle sort of thing, often subject to fate or chance, being an entirely human enterprise…”

Source: Mac Flecknoe (1682), l. 1–2.

Source: The Ribbajack: and Other Haunting Tales

Source: The Roving Mind (1983), Ch. 25
Context: How often people speak of art and science as though they were two entirely different things, with no interconnection. An artist is emotional, they think, and uses only his intuition; he sees all at once and has no need of reason. A scientist is cold, they think, and uses only his reason; he argues carefully step by step, and needs no imagination. That is all wrong. The true artist is quite rational as well as imaginative and knows what he is doing; if he does not, his art suffers. The true scientist is quite imaginative as well as rational, and sometimes leaps to solutions where reason can follow only slowly; if he does not, his science suffers.

Source: Realistic models in probability (1968), p. 1

Source: Time Enough for Love: the lives of Lazarus Long; a novel , (1973), p. 366

Autobiography (1936; 1949; 1958)
Context: Organised religion allying itself to theology and often more concerned with its vested interests than with the things of the spirit encourages a temper which is the very opposite of science. It produces narrowness and intolerance, credulity and superstition, emotionalism and irrationalism. It tends to close and limit the mind of man and to produce a temper of a dependent, unfree person.
Even if God did not exist, it would be necessary to invent Him, so Voltaire, said … perhaps that is true, and indeed the mind of man has always been trying to fashion some such mental image or conception which grew with the mind's growth. But there is something also in the reverse proposition: even if God exist, it may be desirable not to look up to Him or to rely upon Him. Too much dependence on supernatural forces may lead, and has often led, to loss of self-reliance in man, and to a blunting of his capacity and creative ability. And yet some faith seems necessary in things of the spirit which are beyond the scope of our physical world, some reliance on moral, spiritual, and idealistic conceptions, or else we have no anchorage, no objectives or purpose in life. Whether we believe in God or not, it is impossible not to believe in something, whether we call it a creative life-giving force, or vital energy inherent in matter which gives it its capacity for self-movement and change and growth, or by some other name, something that is as real, though elusive, as life is real when contrasted with death. <!-- p. 524 (1946)

Source: Infinite in All Directions (1988), Ch. 1 : In Praise of Diversity
Context: Science and religion are two human enterprises sharing many features. They share these features also with other enterprises such as art, literature and music. The most salient features of all these enterprises are discipline and diversity. Discipline to submerge the individual fantasy in a greater whole. Diversity to give scope to the infinite variety of human souls and temperaments. Without discipline there can be no greatness. Without diversity there can be no freedom. Greatness for the enterprise, freedom for the individual — these are the two themes, contrasting but not incompatible, that make up the history of science and the history of religion.

An Old Chaos: Frozen Horses and Deserts of Brick (p. 25)
The Silence of Animals: On Progress and Other Modern Myths (2013)

Book I, Ch. 1. That Men by various Ways arrive at the same End
Essais (1595), Bartlett's Familiar Quotations, 10th ed. (1919)