The Maupertuis-Koenig affair

In 1751 Samuel Koenig claimed that the principle of least action was not Maupertuis's, and that Leibniz had stated it in a letter of 1707. The dispute that followed ran for years, drew in Euler, Voltaire and Frederick the Great, and ended a reputation.

This page sets out the dispute. It does not deliver a verdict, and the reason is given at the end.

The claim

Koenig, a mathematician and a member of the Berlin Academy over which Maupertuis presided, published a paper questioning the principle. Two claims were bundled together in it, and separating them matters.

The first was mathematical: that the principle as Maupertuis stated it was wrong.

The second was historical: that in so far as it was right, it was Leibniz's, stated in a letter written in 1707.

Koenig quoted the letter. He did not produce it. He had a copy, and said the original was elsewhere.

The response

The Berlin Academy, with Maupertuis presiding and Euler taking the lead, declared the letter a forgery.

Euler wrote a paper on the affair. He defended Maupertuis's priority, argued the principle was sound, and treated the Leibniz letter as fabricated.

The proceeding was not a neutral inquiry. The Academy was judging a challenge to its own president, and the man who wrote its case was that president's colleague and appointee.

Voltaire

Voltaire, resident at Frederick's court and by then hostile to Maupertuis, attacked him in print with considerable savagery, and mocked Euler along with him.

Frederick the Great defended Maupertuis and had Voltaire's pamphlet burned. Voltaire left Prussia.

The literary quarrel is better remembered than the scientific one, which is part of why the affair is usually told as a comedy. Its effect on Maupertuis was not comic: his standing did not recover, and he left Berlin some years later in poor health.

What has changed since

Two things, and both cut against the Academy's finding.

The Leibniz letter is now generally regarded as authentic, on the basis of manuscript evidence found after the affair. The Academy's forgery verdict is not sustained.

And Leibniz did have relevant ideas about extremal quantities in nature, though whether they amount to the principle at issue is a separate question from whether the letter is genuine.

So the historical part of Koenig's claim looks better now than it did in 1751, and the Academy's handling of it looks worse.

Why this page stops here

The volume's charter records this reception history as uncomputed, with the work required stated: read the secondary literature on the affair, and the Euler correspondence, before asserting a verdict.

That reading has not been done for this volume.

What is above rests on encyclopedia-level summaries and on references encountered while surveying sources for other pages. That is enough to say what the dispute was about and that the modern view has shifted. It is not enough to say how much of Maupertuis's claim survives modern scholarship, which is the question the charter actually asks.

So the page states the dispute and stops. The verdict is UNCOMPUTED, and its kind of block is computation: the material is reachable, and the reading has not been performed. See Sources.

This is a deliberate choice rather than an omission. A confident narrative would be easy to write and would be worth nothing, because it would rest on the same tertiary summaries every other confident narrative rests on.

What can be said without the reading

Three things are safe, and they are worth stating because they bear on the rest of the volume.

Priority disputes are not settled by academies with an interest. Whatever the truth about the letter, a body chaired by the accused party's beneficiary was not the right forum, and the finding has not held.

Euler's conduct is the part that ages worst. He was the best mathematician involved by a wide margin, he had an independent and better-founded claim of his own, and he spent his authority defending someone else's priority in a proceeding he should not have been part of. His mathematics on Euler and the Methodus inveniendi is untouched by this. His judgement is not.

The dispute was about the wrong thing. Both sides argued over who first said that nature minimises action. Nature does not minimise action. Within a century Hamilton would correct the word, and within two the quantum account on the Feynman path integral would remove the idea of nature choosing anything at all.

The priority being fought over was priority in a formulation that turned out to be wrong in its central word.

Where to go next

The next development is Lagrange's, and it is at Lagrange and the Mecanique analytique.

Provenance: nothing on this page is quoted from a primary source. Koenig's paper, Euler's paper on the affair, the Leibniz letter and Voltaire's pamphlets are not sources of this volume, and no words are attributed to any of them. The verdict on the priority question is UNCOMPUTED. See Sources.