The provenance of the contemporary pragmatist philosophy of science is 1932 Nobel-laureate physicist Werner Heisenberg’s reflections on the language in his quantum-theory revolution in microphysics. There have been various alternative semantics and thus ontologies proposed for the quantum theory. Most physicists today have accepted one that has ambiguously been called the “Copenhagen interpretation”.
There are two versions of the Copenhagen interpretation. Contrary to the alternative “hidden variables” view of David Bohm, both Copenhagen versions assert a thesis called “duality”. The duality thesis is that the wave and particle manifestations of the electron are two aspects of the same entity, as Heisenberg says, rather than two separate entities, as Bohm says.
1922 Nobel-laureate Niels Bohr, founder of the Copenhagen Institute for Physics, proposed a version called “complementarity”. His version says that the mathematical equations of quantum theory must be viewed instrumentally instead of descriptively, because only ordinary discourse and its refinement in the language of classical physics can describe physical reality. Instrumentalism is the doctrine that scientific theories are not descriptions of reality, but are merely useful linguistic instruments that enable correct predictions.
The quantum theory says that the electron has both wave and particle properties, but in classical physics the semantics of the terms “wave” and “particle” are mutually exclusive – a wave is spread out in space while a particle is a concentrated point. Therefore Bohr maintained that description of the electron’s duality as both “wave” and “particle” is an indispensable semantic antilogy that he called “complementarity”.
Heisenberg, a colleague of Bohr at the Copenhagen Institute, proposed his own version of the Copenhagen interpretation. His version also contains the idea of the wave-particle duality, but he said that the mathematical expression of the quantum theory is realistic and descriptive rather than merely instrumental. And since the equations describing both the wave and particle properties of the electron are mathematically consistent, he disliked Bohr’s complementarity antilogy.
Years later Yale University’s Russell Hanson said that Bohr maintained a “naïve epistemology”. Duality is a thesis in physics while complementarity is a thesis in linguistics and philosophy of language. However, the term “complementarity” has since acquired some conventionality to signify duality, and is now ambiguous as to the issue between Bohr and Heisenberg, since physicists typically disregard the linguistic issue.
These two versions of the Copenhagen interpretation differ in their philosophy of language. Bohr’s philosophy is called a “naturalistic” view of semantics, which requires what in his Atomic Physics and the Description of Nature (1934) he called “forms of perception”. Heisenberg’s philosophy is called an “artifactual” or a “conventionalist” view of semantics, in which the equations of the quantum theory supply the linguistic context, which defines the concepts that the physicist uses for observation.
1921 Nobel-laureate physicist Albert Einstein had influenced Heisenberg’s philosophy of language, which has been incorporated into the contemporary pragmatist philosophy of language. And consistent with his relativized semantics Heisenberg effectively practiced ontological relativity and maintained that the quantum reality exists as “potentia” prior to determination by execution of a measurement operation. For Heisenberg indeterminacy is real. For more about Heisenberg and quantum theory the reader is referred to BOOKs II and IV below.
Contemporary pragmatism is a general philosophy for all empirical sciences, both social and natural sciences. The distinctive linguistic philosophy of Einstein and especially Heisenberg as incorporated into the contemporary pragmatist philosophy of science can be summarized in three theses, which may be taken as basic principles in contemporary pragmatism:
Thesis I: Relativized semantics.
The seminal work is “Quantum Mechanics and a Talk with Einstein (1925-1926)” in Heisenberg’s Physics and Beyond. There Heisenberg relates that in April 1925, when he presented his matrix-mechanics to the prestigious Physics Colloquium at the University of Berlin, Einstein, who was in the assembly, afterward invited him to chat in his home that evening. In their conversation Einstein said that he no longer accepts the positivist view of observation including such positivist ideas as operational definitions. Instead he issued the aphorism: “the theory decides what the physicist can observe”.
Einstein’s view of observation contradicts the fundamental positivist thesis that there is a dichotomous separation between the semantics of observation language and that of theory language. Positivists believed that the objectivity of science requires that the vocabulary and semantics used for incorrigible observation must be uncontaminated by the vocabulary and semantics of speculative and provisional theory.
In the next chapter titled “Fresh Fields (1926-1927)” in the same book Heisenberg reports that Einstein’s discussion with him in Berlin had later occasioned his own reconsideration of observation. Heisenberg recognized that classical Newtonian physical theory had led him to conceptualize the observed track of the electron as continuous in the cloud chamber – an instrument for microphysical observation developed by 1927 Nobel-laureate C.T.R. Wilson – and to misconceive the electron as simultaneously having a definite position and momentum like all Newtonian bodies in motion.
Recalling Einstein’s aphorism that the theory decides what the physicist can observe, Heisenberg reconsidered what is observed in the cloud chamber. Einstein had failed to apply his aphorism to quantum theory, and rejected duality. But Heisenberg rephrased his question about the electron tracks in the cloud chamber using the concepts of the new quantum theory instead of those of the classical Newtonian theory. He reports that he asked himself: Can the quantum mechanics represent the fact that an electron finds itself approximately in a given place and that it moves approximately at a given momentum? In answer to this newly formulated question he found that these approximations could be represented mathematically. He then developed this mathematical representation, which he called the “uncertainty relations”, the historic contribution for which he received the Nobel Prize in 1932.
Russell Hanson expressed Einstein’s aphorism that the physical theory decides what the physicist can observe by saying observation is “theory-laden” and likewise Karl Popper by saying it is “theory-impregnated”.
Paul Feyerabend also recognized employment of relativized semantics to create new observation language for discovery, and he called the practice “counterinduction”. Feyerabend found that Galileo had practiced counterinduction in the Dialogue Concerning the Two Chief World Systems (1632), where Galileo reinterpreted apparently falsifying observations in common experience by using the concepts of the heliocentric theory instead of the concepts of the geocentric theory. Likewise Heisenberg also practiced counterinduction to reconceptualize the perceived sense stimuli observed as the electron track in the cloud chamber by using quantum concepts instead of classical Newtonian concepts.
“Counterinduction” is using the semantics of an apparently falsified theory to revise the test-design language that had supplied the semantics of the descriptive language for the falsifying observations, and thereby to produce new observation language.
Like Einstein, contemporary pragmatists say that the theory decides what the scientist can observe. Thus semantics is relativized in the sense that the meanings of descriptive terms used for reporting observations are not just names or labels for phenomena, but rather are determined by the context in which they occur. More specifically in “Five Milestones of Empiricism” in his Theories and Things the pragmatist philosopher of language Willard van Quine says that the meanings of words are abstractions from the truth conditions of the sentences that contain them, and that it was this recognition of the semantic primacy of sentences that give us contextual definition.
Most notably the defining context includes universal statements that proponents believe are true. The significance is that the acceptance of a new theory superseding an earlier one and sharing some of the same descriptive