There are two principles ...

There are two principles inherent in the very nature of things, recurring in some particular embodiments whatever field we explore - the spirit of change, and the spirit of conservation. There can be nothing real without both. Mere change without conservation is a passage from nothing to nothing. . . . Mere conservation without change cannot conserve. For after all, there is a flux of circumstance, and the freshness of being evaporates under mere repetition.
There are two principles inherent in the very nature of things, recurring in some particular embodiments whatever field we explore - the spirit of change, and the spirit of conservation. There can be nothing real without both. Mere change without conservation is a passage from nothing to nothing. . . . Mere conservation without change cannot conserve. For after all, there is a flux of circumstance, and the freshness of being evaporates under mere repetition.
 Alfred North Whitehead

Quotes from the same author

The art of progress is to preserve order amid change, and to preserve change amid order.
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 Alfred North Whitehead
It does not matter what men say in words, so long as their activities are controlled by settled instincts. The words may ultimately destroy the instincts; but until this has occurred, words do not count.
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 Alfred North Whitehead
Inventive genius requires pleasurable mental activity as a condition for its vigorous exercise. "Necessity is the mother of invention" is a silly proverb. "Necessity is the mother of futile dodges" is much closer to the truth. The basis of growth of modern invention is science, and science is almost wholly the outgrowth of pleasurable intellectual curiosity.
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 Alfred North Whitehead
The essence of Christianity is the appeal to the life of Christ as a revelation of the nature of God and of God's agency in the world. The record is fragmentary, inconsistent, and uncertain. . . . But there can be no doubt as to what elements in the record have evoked a response from all that is best in human nature. The Mother, the Child, and the bare manger: the lowly man, homeless and self-forgetful, with his message of peace, love, and sympathy: the suffering, the agony, the tender words as life ebbed, the final despair: and the whole with the authority of supreme victory.
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 Alfred North Whitehead
Intelligence is quickness to apprehend as distinct form ability, which is capacity to act wisely on the thing apprehended.
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 Alfred North Whitehead