Maupertuis had very little judgment; so far from attempting to conciliate Voltaire, he was rash enough to provoke hostilities.  It was very natural that he should have lost his temper.  He had been for five years the dominating figure in the royal circle, and now suddenly he was deprived of his pre-eminence and thrown completely into the shade.  Who could attend to Maupertuis while Voltaire was talking?—­Voltaire, who as obviously outshone Maupertuis as Maupertuis outshone La Mettrie and Darget and the rest.  In his exasperation the President went to the length of openly giving his protection to a disreputable literary man, La Beaumelle, who was a declared enemy of Voltaire.  This meant war, and war was not long in coming.

Some years previously Maupertuis had, as he believed, discovered an important mathematical law—­the ‘principle of least action.’  The law was, in fact, important, and has had a fruitful history in the development of mechanical theory; but, as Mr. Jourdain has shown in a recent monograph, Maupertuis enunciated it incorrectly without realising its true import, and a far more accurate and scientific statement of it was given, within a few months, by Euler.  Maupertuis, however, was very proud of his discovery, which, he considered, embodied one of the principal reasons for believing in the existence of God; and he was therefore exceedingly angry when, shortly after Voltaire’s arrival in Berlin, a Swiss mathematician, Koenig, published a polite memoir attacking both its accuracy and its originality, and quoted in support of his contention an unpublished letter by Leibnitz, in which the law was more exactly expressed.  Instead of arguing upon the merits of the case, Maupertuis declared that the letter of Leibnitz was a forgery, and that therefore Koenig’s remarks deserved no further consideration.  When Koenig expostulated, Maupertuis decided upon a more drastic step.  He summoned a meeting of the Berlin Academy of Sciences, of which Koenig was a member, laid the case before it, and moved that it should solemnly pronounce Koenig a forger, and the letter of Leibnitz supposititious and false.  The members of the Academy were frightened; their pensions depended upon the President’s good will; and even the illustrious Euler was not ashamed to take part in this absurd and disgraceful condemnation.

Voltaire saw at once that his opportunity had come.  Maupertuis had put himself utterly and irretrievably in the wrong.  He was wrong in attributing to his discovery a value which it did not possess; he was wrong in denying the authenticity of the Leibnitz letter; above all he was wrong in treating a purely scientific question as the proper subject for the disciplinary jurisdiction of an Academy.  If Voltaire struck now, he would have his enemy on the hip.  There was only one consideration to give him pause, and that was a grave one:  to attack Maupertuis upon this matter was, in effect, to attack the King.  Not only was Frederick certainly privy to Maupertuis’