As we already discussed in Realists vs Antirealists (Part I): the Antirealist interpretation, today we’ll talk about the other side of the coin.

The Realist Interpretation:

 Einstein, as a realist, rejected each of the antirrealist claims and replaced them with ones of his own.

-Realist claim 1:
An objective reality exists whether or not human beings exist or know its features.

Philosophers refer to this claim as “metaphysical realism”. According to it, something can exist even if we human beings do not know that it exists. The question whether something actually exists in objective reality is said to be an “ontological” question. The question whether something is known or perceived to exist is said to be an “epistemological” question. Einstein held that it was a grave mistake to confuse ontological questions with epistemological ones.
Thus he wrote: “[the scientist] seeks to describe a world independent of the acts of perception”

-Realist claim 2:
It is the business of physics to give true descriptions of objectively existing objects such as the moon.
Philosophers refer to this sort of claim as “scientific realism”. According to Einstein, the whole purpose of science is to get behind the phenomena of experimental data and their mathematical description to the real world that underlies them. As he put it, “Reality is the business of physics”. He believed, to the end, that the goal of science was to discover the way the world really is as opposed to our perceptions and conceptions of it, and that orthodox quantum theory had not only failed to achieve such a goal but had prematurely abandoned any such quest.

One of the Solvay Conferences:  These guys liked to argue...

One of the Solvay Conferences: These guys liked to argue…

This realist theory of truth is opposed to certain other theories of truth, for example to the so-called “pragmatist” or “instrumentalist” theory according to which a statement is accepted as true if and only if it is useful to accept it. Many of Einstein’s antirealist opponents seem to have adopted a pragmatist theory. They held that physical theories, such as those of quantum mechanics, are to be regarded as true just in so far as the mathematical description of quantum phenomena provides a useful instrument for prediction and explanation. Niels Bohr, in particular, seems to have thought of quantum theory in this sort of way when he wrote: “There is no quantum world. There is only an abstract [mathematical] description.”

-Realist claim 3: Microphysical particles, like atoms and their constituents, and macrophysical objects, like the moon, may exist whether or not they are being observed.

To repeat the third sentence in the passage just quoted, Einstein held that, in physics . . . A spatial position (relative to the co-ordinate system used) is attributed to, say, the moon at any definite time, quite independently of the question whether observations of this position are made or not.
Einstein’s realism (metaphysical, scientific, and semantic) was, and still is, shared by a number of other great physicists. Among them can be listed: Max Planck, Erwin Schrodinger, Louis de Broglie, and – much later – David Bohm. In Einstein’s view, the antirealist beliefs of physicists who adopted the Copenhagen interpretation were akin to those of a religion that is based more on faith than on evidence. As he put it, disparagingly: The Heisenberg-Bohr tranquilizing philosophy – or religion? – is so delicately contrived that, for the time being, it provides a gentle pillow for the true believer from which he cannot very easily be aroused. So let him lie there.

Ezequiel López López

 (Original: Does the moon exists when nobody is looking at it? – Ray Bradley)