At Belmont, the Prince of Arragon has arrived to try his luck at choosing the correct casket, and before he decides on one, he promises Portia that he will abide by her father's rules. First, if he fails to choose the casket containing her portrait, he will never reveal which casket he chose; second, he promises never to court another woman; and last, he will leave Belmont immediately.
Reviewing the inscriptions, he rejects the lead casket immediately because he thinks that it is not beautiful enough to give and risk all his possessions for. He also rejects the gold casket because "what many men desire" may place him on the same level with "the barbarous multitudes." He thus chooses the silver casket, which bears the inscription, "Who chooseth me shall get as much as he deserves." Arragon reviews his worth and decides that he "will assume desert" — that is, he feels that he rightfully deserves Portia. When he opens the silver casket, he finds within "the portrait of a blinking idiot" — a picture of a fool's head. He protests the contents; he chose according to what he felt that he deserved: "Did I deserve no more than a fool's head?" Portia reminds him that no man is permitted to judge his own cause. The scroll in the silver casket reads, "There be fools alive, I wis [know], / Silver'd o'er; and so was this." Arragon departs then with his followers, promising to keep his oath.
Portia is dearly relieved and sums up the reason for the prince's failure: "O, these deliberate fools! When they do choose, / They have their wisdom by their wit to lose." In other words, even fools choose deliberately and believe that they are wise to deliberate; in fact, it is their excessive deliberation which ultimately defeats them.
A servant announces the arrival of a Venetian ambassador from another suitor and adds that he brings gifts; in fact, in the messenger's estimation, the man who accompanies this latest suitor is "so likely an ambassador of love" that "a day in April never came so sweet." Portia is neither impressed nor optimistic, yet she urges Nerissa to bring the man to her so that she can see for herself this "quick Cupid's post [messenger] that comes so mannerly." Nerissa sighs; "Lord Love," she prays, "if thy will it be," let this suitor be Bassanio!
This scene focuses on the Prince of Arragon's choice of the three caskets. The Prince of Morocco's choice was straightforward and simple. He chose the gold casket; it seemed to be the most obvious, most desirable choice. In contrast, the Prince of Arragon's choice is done with more prudence. The prince is a proud man; he seems older than Morocco and almost bloodless, compared to Morocco's fiery charismatic bearing. Often, Shakespeare makes his characters' names suggest their primary qualities; here, "Arragon" was probably chosen for its resemblance to "arrogant." At any rate, Arragon is arrogant, a temperament befitting a Spanish grandee of noble blood, a familiar and conventional figure on the Elizabethan stage.
Once again, we hear the ambiguous inscriptions read for us, and we ourselves puzzle over the enigma of the metals and their relationship to the inscriptions. Arragon considers the caskets, but he does not make Morocco's obvious choice. If gold represents "what many men desire," then Arragon's powerful belief in his own superiority to "the fool multitude that choose by show" makes him reject it. We can agree with that logic, but we have to reject his reasoning ultimately because it is based on his absolute assumption of his own superiority to the multitude.
The silver inscription, "Who chooseth me shall get as much as he deserves," has an immediate appeal for Arragon. It prompts his observations on "merit" (35-48), in which he laments the fact that there is so much "undeserved dignity" in the world; he means those who are given honor without coming by it legitimately, through the "true seed" of noble inheritance. The man is a snob; he has absolutely no doubts about what he deserves, and since his nobility is inherited nobility, he can safely (he thinks) choose the silver casket and "assume desert."
A factor that we should be aware of in this entire scene is an absence of any evidence that Arragon has any love, or even any affection, for Portia. Portia is "deserved." Nowhere can we discern even an inkling of any craving for her. As was noted, the prince is rather bloodless.
In the suitors' choice of the caskets, we have yet another variation of the illusion-reality theme: Gold and silver appear to be the obvious choices to the first two suitors, whose motives for choosing are in some way flawed; neither of them is truly in love with Portia, for example. Yet Bassanio, who does love Portia, will choose the casket which appears to be the least valuable; in reality, it will turn out to be the most valuable. Thus the ability to choose and to distinguish between what appears to be valuable and what really is valuable depends not so much on intelligence — Shylock is far more intelligent than Antonio or Bassanio — but on something deeper and more intangible. In this play, that certain intangible something is love; it is not glory (Morocco), nor nobility of social position (Arragon), nor wealth (Shylock), but love for another human being, which Bassanio and Portia clearly offer to one another.
At this point, the love plot in the play becomes very much like a fairy tale — the beautiful princess is won by love, not by wealth or rank or by calculation; we are reminded of Nerissa's comment in Act I, Scene 2: The proper casket will "Never be chosen by any rightly but one who you shall rightly love." We now know which casket is the right one, and thus we can relax and enjoy the drama of Bassanio's momentous choice. His approach (preceded by "an ambassador of love") is now announced by a messenger, and the fulfillment of the play's love story is clearly anticipated in Nerissa's comment: "A day in April never came so sweet / To show how costly summer was at hand."