Pierre Duhem: Realist or anti-realist?

Pierre Duhem

Pierre Duhem (1861-1916) can be considered one of the last nineteenth-century physicists. Specialist in Thermodynamics, the branch of physics that dominated the second half of the nineteenth century, introduced the idea of the ​​chemical potential at the same time as William Gibbs, expressed in the Gibbs-Duhem equation, which connects the chemical potential with magnitudes such as the volume, pressure, entropy and temperature of a chemical mixture. He is considered one of the creators of physical chemistry and was nominated twice for the Nobel Prize in Physics.

In his scientific work, Duhem confronted Marcellin Berthelot, whose principle of maximum work he opposed. This led to his doctoral thesis being rejected, and he was denied a teaching position at the University of Paris. Duhem was finally shown to be right, as Berthelot’s principle is not generally applicable, for it has many exceptions.

Duhem did not participate directly in the revolution that affected physics in the late nineteenth and early twentieth centuries: the discovery of radioactivity (Becquerel, 1896), quantum theory (Planck, 1900), and the theory of relativity (Einstein, 1905). In his later years, he devoted himself to the study of the history and philosophy of physics, publishing works as important as La Théorie physique. Son objet et sa structure (1906) and Le Système du monde. Histoire des doctrines cosmologiques, de Platon à Copernic (in 10 volumes, 1913-1958).

Nicole Oresme

In these books, in his study of the history of mechanics, Duhem discovered the importance of the work of the XIV century School of Paris, with such important names as Jean Buridan (1300-1358), Nicole Oresme (1323-1382) and Albert of Saxony (1316-1390), who anticipated many of the discoveries later attributed to Galileo, which led the philosophers of the so-called Enlightenment to assert wrongly that the Catholic Church had always opposed science.

Duhem was subject to scientific oblivion during most of the 20th century, probably as a consequence of his religious beliefs (he was a practicing Catholic) and his opposition to the dominant ideology, until his work and life were divulged by Stanley L. Jaki, since 1985.

Let us go back to the question in the title of this post. Was Duhem realist, or anti-realist? The answer is not obvious, as both sides have claimed him for their ranks.

It has been said that Duhem was instrumentalist: in fact, the English Wikipedia affirms it bluntly. The French Wikipedia, on the other hand, denies it categorically in a well-reasoned section, and ascribes his philosophy of physics to phenomenalism. In the first case, Duhem would have been anti-realistic; in the second, he would be a moderate realist. Let us compare these two philosophical theories:

• Instrumentalism asserts that scientific theories do not represent reality. They are just tools that help us adapt to the world and make useful, but untrue, predictions. John Dewey, one of the creators of pragmatic philosophy, can be considered one of the main defenders of this position.
• Phenomenalism, in the style of Immanuel Kant, argues that although phenomena are the only things we can know, they conceal a reality that, although beyond our reach, actually exists. Our theories get progressively near to this reality, without ever reaching it.

That Duhem was a supporter of phenomenalism rather than instrumentalism, can be deduced from his writings. In particular, let's look at this quote from his book La Théorie physique, mentioned above:

It is vain to insist on this idea, that theories have no power to grasp reality, that they are just good to give experimental laws a summarized and classified representation; one cannot force oneself to believe that a system capable of ordering so simply and so easily a huge number of laws, at first sight so disparate, is a purely artificial system; by an intuition where Pascal would have recognized one of those reasons of the heart that reason does not know, one must affirm one’s faith in a real order of which our theories are an image, every day clearer and more faithful.

In the same vein, Duhem expresses distrust about scientific theories not based on facts, just on speculations, something quite common in our time, as I commented in another post in this blog. This attitude, clearly realistic, was expressed near the end of his life in a speech to the Catholic Female Students Association of the University of Bordeaux:

Sometimes... the reasoning spirit is fooled into the game of unfounded deductions; it enjoys climbing the rigid and trembling stairs of theories; it does not examine whether such fragile scaffolding rests on secure foundations... it is soon seized by vertigo; it falls into the vaguest pantheisms, into the most nebulous mysticisms.

Willard Quine

I wonder if Duhem was thinking about Einstein when he said these words.

Further proof that Duhem was a moderate realist and not an anti-realist (or at least an instrumentalist) is the fact that analytic philosophy recognizes a Duhem-Quine thesis, which unites his name with that of Willard Quine (1908-2000), mentor of Hilary Putnam (1916-2016), the creator of the realist no-miracles argument, to which the two previous posts were dedicated. In my opinion, these three thinkers, who cover a century and a half of history, must be ascribed together to a moderate realist position.

The same post in Spanish
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Manuel Alfonseca