Pierre Duhem, Popper’s predecessor

Karl Popper

In a previous post in this blog, I mentioned how Karl Popper defines what is, and what is not, a scientific theory:

A theory is scientific if and only if it is possible to design an experiment that demonstrates that this theory is false.

I also said there that, according to Popper, a scientific theory can never be considered completely confirmed. In other words, we can never be absolutely sure that it is true.

After writing that post, which I published almost one year ago, I have discovered that these two Popper’s fundamental ideas had been anticipated by Pierre Duhem, to whom I dedicated the previous post in this blog.

Popper detailed both these ideas in his book The Logic of Scientific Research, published in German in 1934 and in English in 1959, both versions written by himself. Duhem, however, had anticipated them in 1913, in a letter addressed to Réginald Garrigou-Lagrange, which the latter published in his book Dieu. Son existence et sa nature (1914). By then, Popper was about 12 years old. Did Popper read Duhem? Perhaps not this letter, although other works certainly, since in The Logic of Scientific Research he quotes Duhem five times, usually to show his discrepancy. The problem is that misunderstanding Duhem is quite easy. To avoid it, one should probably read his whole work, which not everybody can do.

Let us look at what Duhem wrote in that letter, the most reprinted of his writings, for Garrigou-Lagrange’s book saw 14 editions, and the letter was reprinted separately by Stanley L. Jaki in Scientist and Catholic: Pierre Duhem (1990).

1.      We will never have the right to assert categorically that any principle of the mechanical and physical theory is TRUE.

2.      None of the principles on which the mechanical and physical theory is based can be said to be FALSE, unless phenomena have been discovered in disagreement with the consequences of deductions that have that principle as one of the premises.

Pierre Duhem

If you read carefully these two statements, you will see that Popper's ideas were prefigured in them.

Coming back to my post about Duhem last week, where I discussed whether his ideas were realist or anti-realist within the framework of the four main theories on the subject, which I detailed in another post, we can deduce the following:

• From the first statement, it follows that Duhem does not defend the realism of truth, for he denies that scientific theories can ever be true.
• From the second, it follows that Duhem does not follow the most extreme version of anti-realism, which holds that we have reasons to affirm that the entities postulated by science do not exist.  In other words, it holds that all scientific theories are false.

Taking into account Duhem’s quotation in my previous post, we should classify him among those who defend the realism of entities, those who say that our theories refer to an underlying reality that actually exists, although such theories can be mistaken.

The same post in Spanish
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Manuel Alfonseca