Editing Arthur Eddington (section)

===Idealism===
{{more citations needed section|date=May 2016}}
Eddington wrote in his book ''The Nature of the Physical World'' that "The stuff of the world is mind-stuff."
{{Blockquote|The mind-stuff of the world is, of course, something more general than our individual conscious minds ... The mind-stuff is not spread in space and time; these are part of the cyclic scheme ultimately derived out of it ... It is necessary to keep reminding ourselves that all knowledge of our environment from which the world of physics is constructed, has entered in the form of messages transmitted along the nerves to the seat of consciousness ... Consciousness is not sharply defined, but fades into subconsciousness; and beyond that we must postulate something indefinite but yet continuous with our mental nature ... It is difficult for the matter-of-fact physicist to accept the view that the substratum of everything is of mental character. But no one can deny that mind is the first and most direct thing in our experience, and all else is remote inference.|Eddington, ''The Nature of the Physical World'', 276–81.}}

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 behaviour 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, since the disjunction of materialism or idealism are assumed to be 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.

Eddington believed that physics cannot explain [[consciousness]] - "light waves are propagated from the table to the eye; chemical changes occur in the retina; propagation of some kind occurs in the optic nerves; atomic changes follow in the brain. Just where the final leap into consciousness occurs is not clear. We do not know the last stage of the message in the physical world before it became a sensation in consciousness".<ref>{{cite book |last1=De Konick |first1=Charles |title=The Writings of Charles De Koninck Volume 1 |date=2016 |publisher=University of Notre Dame Press}}</ref>

[[Ian Barbour]], in his book ''Issues in Science and Religion'' (1966), p.&nbsp;133, cites Eddington's ''The Nature of the Physical World'' (1928) for a text that argues the [[Werner Heisenberg|Heisenberg]] [[uncertainty principle]] 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 (philosophy)|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.<ref name="de Koninck">{{Cite book
| publisher = University of Notre Dame Press
| isbn = 978-0-268-02595-3
| last = de Koninck
| first = Charles
| author-link=Charles De Koninck
| title = The Writings of Charles de Koninck
| location = Notre Dame, Ind.
| date = 2008
| oclc = 615199716
| chapter = The philosophy of Sir Arthur Eddington and The problem of indeterminism
}}</ref> As De Koninck quotes Eddington,

{{Blockquote|There is a doctrine well known to philosophers that the moon ceases to exist when no one is looking at it. I will not discuss the doctrine since I have not the least idea what is the meaning of the word existence when used in this connection. At any rate the science of astronomy has not been based on this spasmodic kind of moon. In the scientific world (which has to fulfill functions less vague than merely existing) there is a moon which appeared on the scene before the astronomer; it reflects sunlight when no one sees it; it has mass when no one is measuring the mass; it is distant 240,000 miles from the earth when no one is surveying the distance; and it will eclipse the sun in 1999 even if the human race has succeeded in killing itself off before that date.|Eddington, ''The Nature of the Physical World'', 226}}