Arthur Eddington : biography
During the 1920s and 30s Eddington gave innumerable lectures, interviews, and radio broadcasts on relativity (in addition to his textbook The Mathematical Theory of Relativity), and later, quantum mechanics. Many of these were gathered into books, including The Nature of the Physical World and New Pathways in Science. His skillful use of literary allusions and humor helped make these famously difficult subjects quite accessible.
Eddington’s books and lectures were immensely popular with the public, not only because of Eddington’s clear and entertaining exposition, but also for his willingness to discuss the philosophical and religious implications of the new physics. He argued for a deeply-rooted philosophical harmony between scientific investigation and religious mysticism, and also that the positivist nature of modern physics (i.e., relativity and quantum physics) provided new room for personal religious experience and free will. Unlike many other spiritual scientists, he rejected the idea that science could provide proof of religious propositions. He promoted the infinite monkey theorem in his 1928 book The Nature of the Physical World, with the phrase "If an army of monkeys were strumming on typewriters, they might write all the books in the British Museum". His popular writings made him, quite literally, a household name in Great Britain between the world wars.
Sir Arthur Eddington wrote in his book The Nature of the Physical World that "The stuff of the world is mind-stuff."
The idealist conclusion was not integral to his epistemology but was based on two main arguments.
The first derives directly from current physical theory. Briefly, mechanical theories of the ether and of the behavior of fundamental particles have been discarded in both relativity and quantum physics. From this Eddington inferred that a materialistic metaphysics was outmoded and that, in consequence—the disjunction of materialism or idealism being assumed exhaustive—an idealistic metaphysics is required. The second and more interesting argument was based on Eddington’s epistemology and may be regarded as consisting of two parts. First, all we know of the objective world is its structure, and the structure of the objective world is precisely mirrored in our own consciousness. We therefore have no reason to doubt that the objective world, too, is "mind-stuff." Dualistic metaphysics, then, cannot be evidentially supported.
But, second, not only can we not know that the objective world is nonmentalistic, we also cannot intelligibly suppose that it could be material. To conceive of a dualism entails attributing material properties to the objective world. However, this presupposes that we could observe that the objective world has material properties. But this is absurd, for whatever is observed must ultimately be the content of our own consciousness and, consequently, nonmaterial.
Ian Barbour in his book Issues in Science and Religion (1966), p. 133, cites Arthur Eddington’s The Nature of the Physical World (1928) for a text that argues The Heisenberg Uncertainty Principles provides a scientific basis for "the defense of the idea of human freedom" and his Science and the Unseen World (1929) for support of philosophical idealism "the thesis that reality is basically mental".
Charles De Koninck points out that Eddington believed in objective reality existing apart from our minds, but was using the phrase "mind-stuff" to highlight the inherent intelligibility of the world: that our minds and the physical world are made of the same "stuff" and that our minds are the inescapable connection to the world. As De Koninck quotes Eddington,
Against Albert Einstein and others who advocated determinism, indeterminism—championed by Eddington—says that a physical object has an ontologically undetermined component that is not due to the epistemological limitations of physicists’ understanding. The uncertainty principle in quantum mechanics, then, would not necessarily be due to hidden variables but to an indeterminism in nature itself.