These revelations are, in some sense far, far less than what Sergius and Louka have to admit. Namely, that they have been carrying on a secret flirty relationship, and Sergius’ clear instigation of this while he was engaged to Raina. This, and not Raina’s love for Bluntschli, is the primary infidelity of the play. Sergius’s flirtation with Louka is direct and indiscreet, whereas Raina’s love for Bluntschli has only manifested in a picture that Bluntschli does not even know about. Louka has made plain, from the beginning of the play, that she has long desired to end up with a man above her own social rank. For Louka, Nicola is a pawn rather than a fiancé, and Sergius, though in many ways loathsome, represents a path out of poverty and servitude for her.
Notable in this part of Act Three is the speed with which these revelations unfold, and the manner by which characters deal with the information. Petkoff and Catherine are very quick to understand that Bluntschli is a decent man. But it is only when he reveals that he is also extraordinarily wealthy, even more so than the noble Bulgarian Petkoffs, that they acknowledge he is a good match for. This reveals the true values of the Petkoff family, and of nobility more broadly, which was quick to sacrifice its high social standing whenever a large amount of money was involved. This all points to one of the underlying conclusions of the play: that people’s moral codes are not so much fixed as situational, that people must make their decisions based on the information available to them, and whatever comes from those decisions is therefore optimal under the circumstances.
The idea that everyone must behave according to the hand of cards he or she is dealt is the advice Bluntschli gives to Raina at the beginning of the play. It is certainly “bad” of him to threaten Raina at gunpoint if she calls out and reveals him, and it is “good” of him to be nice to her, and to sleep peacefully on her bed. But Bluntschli is really neither “good” nor “bad” in that scene, or in the rest of the play. He is someone who takes in information and does what he can with it to stay alive. If this is self-preservation, it is of a courteous and transparent kind. It might not always inspire devotion, but it does eventually in Raina, who is accustomed to various performances of pride and self-importance, mostly by Sergius, that she realizes are without merit.
Bluntschli, perhaps unintentionally, teaches the Petkoffs and those around them to behave with a degree of moderation, restraint, and shifting ethics that might be combined into a philosophy called “pragmatism” or “rationalism.” What that really means, for Bluntschli, is that the world presents a set of decisions to be made, and that the man best suited to come out on top in such a world is the man who acknowledges that many of those decisions will have bad and worse, rather than good and bad, outcomes. One cannot rant and rail against such a world. One can only do well to accept it, and to move forward without regretting decisions when they come.
This all makes Sergius’s exclamation at the end of the play so poignant, and a fitting summary of the events that passed. Bluntschli is an estimable man precisely because he is the man that, in the beginning of the play, no one seemed very eager to imitate. He was not invested in projecting confidence, heroism, or pride. But it was a sense of collectedness that allowed Bluntschli to survive his first night with Raina, to escape, to return to the Petkoff house ostensibly to return his coat, and finally to win over Raina, for whom he expresses love only after realizing that she very well can be won, and wed, after all.