Do you remember, Marquis, what Monsieur de Coulanges said to us one day? "Constancy is the virtue of people of limited merit. Have they profited by the caprice of an amiable woman to establish themselves in her heart? the sentiment of medicrioty fixes them there, it intimidates them, they dare not make an effort to please others. Too happy at having surprised her heart, they are afraid of abandoning a good which they may not find elsewhere, and, as an instant's attention to their little worth might undeceive this woman, what do they then do? They elevate constancy up among the virtues; they transform love into a superstition; they know how to interest reason in the preservation of a heart which they owe only to caprice, occasion, or surprise." Be on your guard against imitating these shallow personages. Hearts are the money of gallantry; amiable people are the assets of society, whose destiny is to circulate in it and make many happy. A constant man is therefore as guilty as a miser who impedes the circulation in commerce. He possesses a treasure which he does not utilize, and of which there are so many who would make good use of it.
What sort of a mistress is that who is retained by force of reason? What languor reigns in her society, what violence must one not employ to say there is love when it has ceased to exist? It is seldom that passion ceases in both parties at the same time, and then constancy is a veritable tyrant; I compare it to the tyrant of antiquity who put people to death by tying them to dead bodies. Constancy condemns us to the same punishment. Discard such a baleful precedent to the liberty of association.
Believe me, follow your tastes, for the court lady you mentioned; she may weary you at times, it is true, but at least she will not degrade you. If, as you say, she is as little intelligent as she is beautiful, her reign will soon be over. Your place in her heart will soon be vacant, and I do not doubt that another or even several other gallantries will follow yours. Perhaps you will not wait for the end, for I see by your letter that you are becoming a man of fashion. The new system you have adopted makes it certain, nothing can be better arranged. Never finish one affair without having commenced another; never withdraw from the first except in proportion as the second one progresses. Nothing can be better, but in spite of such wise precautions, you may find yourself destitute of any, as, for example, some event beyond the reach of human foresight may interfere with these arrangements, may have for principle always to finish with all the mistresses at once, before enabling you to find any one to keep you busy during the interregnum. I feel free to confess, Marquis, that such an arrangement is as prudent as can be imagined, and I do not doubt that you will be well pleased with a plan so wisely conceived. Adieu.