In Chapter 26, D'Artagnan listens to a conversation between Aramis and two priests. When one of the priests insists that going into the priesthood is a happy renunciation of evil, Aramis points out a fallacy in his logic and uses logos to insist that some regret upon going into the priesthood is appropriate:
“But you must agree,” Aramis went on, “that it would be ungracious to offer the Lord only things we dislike. Isn’t that right, d’Artagnan?”
“It certainly is!” replied his friend.
The curate and the Jesuit started convulsively in their chairs.
“That’s my point of departure,” said Aramis. “It’s a syllogism: the world has its attractions; I’m leaving the world; therefore I’m making a sacrifice. Scripture clearly tells us that we must make a sacrifice to the Lord.”
The priest insists that worldly things (such as sex) are evil. Renouncing these things for God is a trade that he believes is all positive: in the place of evil, a priest welcomes the goodness of God into his life. Aramis struggles with this idea. He points out that if the world is all evil and causes us only unhappiness, it is hardly a gracious "sacrifice" to God. Becoming a priest only means something, he argues, if it involves giving up something else that is good. He calls his reasoning a "syllogism," or an "if...if...then..." conclusion. If he feels he is giving up "the world's attractions" by entering the priesthood, and if sacrifice is what scripture says priests must do, he is acting like a priest by expressing some regret that he will no longer be able to do certain things when he is a priest—and if he didn't feel this regret, he wouldn't be making a true sacrifice.
Aramis's debate with the priest in this scene is ostensibly about his "thesis," the piece of writing about religious doctrine that will qualify him for the priesthood. But it is also clear from his logic that he is ambivalent about entering the priesthood to begin with. He wants to prove that ambivalence makes him even more qualified to be a priest. Sure enough, despite his air of seriousness in this scene, he changes his mind about becoming a priest as soon as d'Artagnan shows him the letter his mysterious mistress left him that morning. Aramis's ability to convince the priests that he is ready to join their ranks when he so clearly is not can be read as an underhanded commentary on the hypocritical and unprincipled world of the clergy. In a novel that details many corrupt schemes of Cardinal Richelieu, this scene makes it clear that priests are experts at convincing themselves that they are behaving in accordance with morality and scripture.