Frederick tells D'Alembert that though the Empress overwhelms Diderot with favours, people at St. Petersburg find him tiresome and disputatious, and "talking the same rigmarole over and over again." In her letters to Voltaire, Catherine lets nothing of this be seen. She finds Diderot's imagination inexhaustible, and ranks him among the most extraordinary men that have ever lived; she delights in his conversation, and his visits have given her the most uncommon pleasure. All this was perhaps true enough. Catherine probably rated the philosopher at his true worth as a great talker and a singular and original genius, but this did not prevent her, any more than it need prevent us, from seeing the limits and measure. She was not one of the weaker heads who can never be content without either wholesale enthusiasm or wholesale disparagement. Diderot had a companion who pleased her better than Diderot himself. Grimm came to St. Petersburg at this time to pay his first visit, and had a great success. "The Empress," wrote Madame Geoffrin to King Stanislas, "lavished all her graces on Grimm. And he has everything that is needed to make him worthy of them. Diderot has neither the fineness of perception, nor the delicate tact that Grimm has, and so he has not had the success of Grimm. Diderot is always in himself, and sees nothing in other people that has not some reference to himself. He is a man of a great deal of understanding, but his nature and turn of mind make him good for nothing, and, more than that, would make him a very dangerous person in any employment. Grimm is quite the contrary."[86] [86] Mouy's _Corresp. du roi Stanislas_, p. 501.