The Duhem-Quine Thesis Reconsidered

The high point of the falsification of physical theories in a standard view of the philosophy of science is the so-called crucial experiment. This experiment is a kind of manipulated empirical test, which provides the criterion for distinguishing between two rival hypotheses, where one is an acceptable theory due to passing the test, and the other turns out to be an unacceptable theory as it does not pass the test. The crucial experiment was supposed to play a significant role because, in virtue of an empirical disconfirmation of one theory, the experiment was assumed to confirm the other as true. However, in 1906, in La théorie physique, son object et la structure (hereafter quoted in English translation as The Aim and Structure of Physical Theory (1906/1954)), Pierre Duhem famously argued against this view and stated that crucial experiments in physics are impossible as they are necessarily ambiguous and logically incomplete. His contention rested on the claim that, “[a] physical theory is not an explanation [of true reality in itself in virtue of some broad metaphysical ramification of physics]. It is a system of mathematical propositions, deduced from a small number of principles, which aim to represent as simply, as completely, and as accurately as possible a set of experimental laws” (ibid., p. 19). Furthermore, different theories could be equally suitable to represent a given group of experimental laws. And, assuming holism, no hypothesis could be tested in isolation, but merely as a part of a set of an entire scientific theory. The problem which Duhem identified in 1906 was slightly overshadowed and neglected in mainstream philosophy of science until the appearance of a challenging paper by Willard Van Orman Quine published in 1951 and entitled “Two Dogmas of Empiricism”. Quine’s paper caused a revival of interest in Duhem’s original formulation and gave a new impulse towards the problem in the form of the so-called Duhem-Quine thesis. The aim of this paper is to reconsider whether Duhem was right to argue that there are no crucial experiments in physics. In order to assess the validity of the thesis, first, this paper makes an exposition of Duhem’s arguments in their favour, and analyses the major criticisms of this position offered in the subject-literature of Adolf Grünbaum, who explicitly attacked the arguments for the thesis as inconclusive and false. Then, this paper presents possible modes of defence of the Duhem-Quine thesis and argues that the original formulation of the thesis is well qualified and plausible. Finally, this paper offers a pragmatic interpretation of the theory choice.

Two Crucial Experiments on the Nature of Light: Beyond the Bounds of Wave-Particle Duality

The wave-particle duality of light has been hanging over the clouds of science as an insuperable mystery. Debates have gone on for centuries as to which of the two aspects of light best represents the natural property of light. On the one hand, the particle theory of light camp made its own submissions a long time ago with many experimental demonstrations to confirm its position. On the other hand, the wave theory of light camp did organize or face some experiments to corroborate its own position. But then, a middle ground interpretation was shoveled-in by Niels Bohr during the second decade of the 20th Century. For him, the two aspects of light are complementary and Louis de Broglie popularized it, despite the halting beginnings of the complementarity Thesis. A double-slit experiment was, however, organized to show that light has these dual aspects. The central thesis of this paper is that though light exhibits these dual aspects, it is fundamentally a wave. The paper adopts the historiographical approach in navigating this lingering issue of the nature of light in the history of science.

Crucial experiments

A ‘crucial experiment’ allegedly establishes the truth of one of a set of competing theories. Francis Bacon (1620) held that such experiments are frequent in the empirical sciences and are particularly important for terminating an investigation. These claims were denied by Pierre Duhem (1905), who maintained that crucial experiments are impossible in the physical sciences because they require a complete enumeration of all possible theories to explain a phenomenon – something that cannot be achieved. Despite Duhem, scientists frequently regard certain experiments as crucial in the sense that the experimental result helps make one theory among a set of competitors very probable and the others very improbable, given what is currently known.

Duhem, Pierre Maurice Marie (1861–1916)

Duhem was a French Catholic physicist, historian of science and philosopher of science. Champion of a programme of generalized thermodynamics as a unifying framework for physical science, he was a pioneer in the history of medieval and renaissance science, where he emphasized a continuity between medieval and early modern science. Duhem was also one of the most influential philosophers of science of his day, thanks to his opposition to mechanistic modes of explanation and his development of a holistic conception of scientific theories, according to which individual empirical propositions are not tested in isolation but only in conjunction with other theoretical claims and associated auxiliary hypotheses. Such a view of theory testing entails that there are no ‘crucial experiments’ deciding unambiguously for or against a given theory and that empirical evidence therefore underdetermines theory choice. Theory choice is thus partly a matter of convention. Duhem’s conventionalism is similar in kind to that later advocated by Otto Neurath and by W.V. Quine.

Was Pierre Duhem an Esprit de finesse?

Although Pierre Duhem is well known for his conventionalist outlook and, in particular, for his critique of crucial experiments outlined in his thesis on the empirical indeterminacy of theory, he also contributed to the scholarship on the psychological profiles of scientists by revising Pascal’s famous distinction between the subtle mind and the geometric mind (esprits fins and esprits géométriques). For Duhem, the ideal scientist is the one who combines the defining qualities of both types of intellect. As a physicist, Duhem made important theoretical contributions to the field of thermodynamics as well as to the then-nascent physical chemistry. Due to his rejection of atomism and his unrelenting critique of Maxwell’s electrodynamics, however, in his later years, Duhem’s work was surpassed and abandoned by the dominant tendencies of physics of the time. In this essay, I will discuss whether Duhem himself can be understood through the lens of his own account of the scientist’s psychological profile. More specifically, I examine whether the subtle mind – to which he seems to assign greater cognitive value – in fact plays a key role in Duhem’s critique of the English School (école anglaise), or if his preference for the axiomatic structure of theoretical physics shows a greater affinity with the geometric mind.