The rules of good breeding, established in the world on this head, seem to have been dictated by a spirit of treachery and falsehood.  To appear the friend of a man when in reality we are no longer so, is to reserve to ourselves the means of doing him an injury by surprising honest men into an error.  I recollected that when the illustrious Montesquieu broke with Father de Tournemine, he immediately said to everybody:  “Listen neither to Father Tournemine nor myself, when we speak of each other, for we are no longer friends.”  This open and generous proceeding was universally applauded.  I resolved to follow the example with Diderot; but what method was I to take to publish the rupture authentically from my retreat, and yet without scandal?  I concluded on inserting in the form of a note, in my work, a passage from the book of Ecclesiasticus, which declared the rupture and even the subject of it, in terms sufficiently clear to such as were acquainted with the previous circumstances, but could signify nothing to the rest of the world.  I determined not to speak in my work of the friend whom I renounced, except with the honor always due to extinguished friendship.  The whole may be seen in the work itself.

There is nothing in this world but time and misfortune, and every act of courage seems to be a crime in adversity.  For that which has been admired in Montesquieu, I received only blame and reproach.  As soon as my work was printed, and I had copies of it, I sent one to Saint Lambert, who, the evening before, had written to me in his own name and that of Madam d’ Houdetot, a note expressive of the most tender friendship.

The following is the letter he wrote to me when he returned the copy I had sent him.

Eaubonne, 10th October, 1758.

“Indeed, sir, I cannot accept the present you have just made me.  In that part of your preface where, relative to Diderot, you quote a passage from Ecclesiastes (he mistakes, it is from Ecclesiasticus) the book dropped from my hand.  In the conversations we had together in the summer, you seemed to be persuaded Diderot was not guilty of the pretended indiscretions you had imputed to him.  You may, for aught I know to the contrary, have reason to complain of him, but this does not give you a right to insult him publicly.  You are not unacquainted with the nature of the persecutions he suffers, and you join the voice of an old friend to that of envy.  I cannot refrain from telling you, sir, how much this heinous act of yours has shocked me.  I am not acquainted with Diderot, but I honor him, and I have a lively sense of the pain you give to a man, whom, at least not in my hearing, you have never reproached with anything more than a trifling weakness.  You and I, sir, differ too much in our principles ever to be agreeable to each other.  Forget that I exist; this you will easily do.  I have never done to men either good or evil of a nature to be long remembered.  I promise you, sir, to forget your person and to remember nothing relative to you but your talents.”