The plot if The Merchant of Venice is certainly advanced as Antonio learns in the first scene of Act III that not one, but two of his ships have met with ruin. With these tremendous financial loses, Antonio will not be able to repay his debt to "the Jew." So, much of the tension of the play lies in Shylock's famous speech with its forceful rhetoric and its purpose of justifying Shylock's brutal violence against Antonio in exacting a pound of flesh from Antonio.
Well, the scene begins with Salerio and Solanio conversing. "This same irritating pair"( Garber, SHAKESPEARE AFTER ALL) also appear in the first scene of the play discussing Antonio's sadness. One then may note when reviewing their conversation with Shylock a multiplicity of possible motives and causes regarding the feelings and actions of both Shylock and Antonio. One critic suggested that Salerio and Solanio are like Tweedledum and Tweedledee(see notes in Wikipedia). When we look again at those two we find the two are not altogether the same (In both scenes Salerio speaks first). Then, one might also sympathize with Morroco and Aragon a bit. In due course, I must note that Salerio's "I for my part knew the tailor that made the wings she flew withal"(3.1.25) is the third of the character's references to birds or flight(see his first speech and Act 2, scene 6). In ROMEO AND JULIET, Romeo's "So shows a snowy dove trooping with crows(ROM1.4.161), Juliet's "For thou wilt lie upon the wings of night/ Whiter than new snow upon a raven's back"(ROM3.2.18-19) and "Dove-feathered raven"(ROM3.2.76) are archetypal images. Shylock's mention of one named Leah is interesting having come across the terms pastoral elegy, a poetic form, in a book someone gave me titled A HANDBOOK TO LITERATURE(by Thrall, Hibbard and Holman).