but it happened to appear at this particular moment, and Voltaire pounced upon it with the swift swoop of a hawk on a mouse.  The famous Diatribe du Docteur Akakia is still fresh with a fiendish gaiety after a hundred and fifty years; but to realise to the full the skill and malice which went to the making of it, one must at least have glanced at the flat insipid production which called it forth, and noted with what a diabolical art the latent absurdities in poor Maupertuis’ reveries have been detected, dragged forth into the light of day, and nailed to the pillory of an immortal ridicule.  The Diatribe, however, is not all mere laughter; there is a real criticism in it, too.  For instance, it was not simply a farcical exaggeration to say that Maupertuis had set out to prove the existence of God by ’A plus B divided by Z’; in substance, the charge was both important and well founded.  ‘Lorsque la metaphysique entre dans la geometrie,’ Voltaire wrote in a private letter some months afterwards, ’c’est Arimane qui entre dans le royaume d’Oromasde, et qui y apporte des tenebres’; and Maupertuis had in fact vitiated his treatment of the ’principle of least action’ by his metaphysical pre-occupations.  Indeed, all through Voltaire’s pamphlet, there is an implied appeal to true scientific principles, an underlying assertion of the paramount importance of the experimental method, a consistent attack upon a priori reasoning, loose statement, and vague conjecture.  But of course, mixed with all this, and covering it all, there is a bubbling, sparkling fountain of effervescent raillery—­cruel, personal, insatiable—­the raillery of a demon with a grudge.  The manuscript was shown to Frederick, who laughed till the tears ran down his cheeks.  But, between his gasps, he forbade Voltaire to publish it on pain of his most terrible displeasure.  Naturally Voltaire was profuse with promises, and a few days later, under a royal licence obtained for another work, the little book appeared in print.  Frederick still managed to keep his wrath within bounds:  he collected all the copies of the edition and had them privately destroyed; he gave a furious wigging to Voltaire; and he flattered himself that he had heard the last of the business.

Ne vous embarrassez de rien, mon cher Maupertuis [he wrote to the President in his singular orthography]; l’affaire des libelles est finie.  J’ai parle si vrai a l’home, je lui ai lave si bien la tete que je ne crois pas qu’il y retourne, et je connais son ame lache, incapable de sentiments d’honneur.  Je l’ai intimide du cote de la boursse, ce qui a fait tout l’effet que j’attendais.  Je lui ai declare enfin nettement que ma maison devait etre un sanctuaire et non une retraite de brigands ou de celerats qui distillent des poissons.

Apparently it did not occur to Frederick that this declaration had come a little late in the day.  Meanwhile Maupertuis, overcome by illness and by rage,