“It is pleasant to observe by what regular gradation we surmount the force of local prejudice as we enlarge our acquaintance with the world.”

The Monthly Magazine

Source: The Sun: A Biography by David Whitehouse, page 225.

This has also appeared in the alternate form: "What we observe is not nature itself, but nature exposed to our method of questioning."
Physics and Philosophy (1958)
Variant: What we observe is not nature itself, but nature exposed to our method of questioning.
Source: Physics and Philosophy: The Revolution in Modern Science

2016, Disabled American Veterans Convention (August 2016)

The Abolition of Work (1985)

1960s, The Quest for Peace and Justice (1964)
Context: Every man lives in two realms, the internal and the external. The internal is that realm of spiritual ends expressed in art, literature, morals, and religion. The external is that complex of devices, techniques, mechanisms, and instrumentalities by means of which we live. Our problem today is that we have allowed the internal to become lost in the external. We have allowed the means by which we live to outdistance the ends for which we live. So much of modern life can be summarized in that arresting dictum of the poet Thoreau: "Improved means to an unimproved end". This is the serious predicament, the deep and haunting problem confronting modern man. If we are to survive today, our moral and spiritual "lag" must be eliminated. Enlarged material powers spell enlarged peril if there is not proportionate growth of the soul. When the "without" of man's nature subjugates the "within", dark storm clouds begin to form in the world.

All the Trouble in the World (1994)

In The Light of what We Know (2014)