“Progress and stability are mutually exclusive.”

2009, A New Beginning (June 2009)

Source: On Liberty

Source: Humanity Comes of Age, A study of Individual and World Fulfillment (1950), Introduction p. I - XII

As quoted in speech by Edward de Veaux Morrell https://cdn.loc.gov/service/rbc/lcrbmrp/t2609/t2609.pdf (April 1904)
Variant: In all things that are purely social we can be as separate as the fingers, yet one as the hand in all things essential to mutual progress.

Introductory Essay-Christian Psalmist,or Hymns Selected & Original (1825).
Other

Source: Program On Human Effectiveness, 1996, https://web.stanford.edu/dept/SUL/library/extra4/sloan/mousesite/Archive/Post68/PrHumanEffectiveness.html

Source: Words of a Sage : Selected thoughts of African Spir (1937), p. 44.

Mutual Aid: A Factor of Evolution (1902)
Context: As to the sudden industrial progress which has been achieved during our own century, and which is usually ascribed to the triumph of individualism and competition, it certainly has a much deeper origin than that. Once the great discoveries of the fifteenth century were made, especially that of the pressure of the atmosphere, supported by a series of advances in natural philosophy — and they were made under the medieval city organization, — once these discoveries were made, the invention of the steam-motor, and all the revolution which the conquest of a new power implied, had necessarily to follow... To attribute, therefore, the industrial progress of our century to the war of each against all which it has proclaimed, is to reason like the man who, knowing not the causes of rain, attributes it to the victim he has immolated before his clay idol. For industrial progress, as for each other conquest over nature, mutual aid and close intercourse certainly are, as they have been, much more advantageous than mutual struggle.

"Society and Civilization" in the American Review (July 1845)
Context: The duties of man consist in alternate action and meditation, mutually aiding and relieving each other; and both, directed with undeviating aim, to the progressive improvement of himself and his fellow creatures. Heaven has given him in charge, to promote the happiness and well-being of himself, his wife, his children, his kindred, his neighbors, his fellow citizens, his country, and his kind; and the great problem of legislation is, so to organize the civil government of a community, that this gradation of duties, may be made to harmonize in all its parts — that in the operation of human institutions upon social action, self-love and social may be made the same.