What role does the relationship between Jessica and Lorenzo play in the story?

Jessica and Lorenzo have a relationship that differs significantly from the other relationships in the story. The key difference lies in the ex-societal nature of their bond. In the relationships between Bassanio and Portia, as well as between Nerissa and Gratiano, there is a larger community, outside the two consenting parties, that validates the relationship. In the case of Portia, she is not free to marry whom she wills because of the system of selection...

Jessica and Lorenzo have a relationship that differs significantly from the other relationships in the story. The key difference lies in the ex-societal nature of their bond. In the relationships between Bassanio and Portia, as well as between Nerissa and Gratiano, there is a larger community, outside the two consenting parties, that validates the relationship. In the case of Portia, she is not free to marry whom she wills because of the system of selection her father has put in place:

O me, the word choose! I may neither choose who I would, nor refuse who I dislike; so is the will of a living daughter curbed by the will of a dead father. (1.2.25)

The conditions upon which Portia forgives Bassanio at the end of the play show that this theme of accountability to an entity outside the pair exists in the relationship between Bassanio and Portia as well. Portia will not forgive Bassanio until Antonio makes a soul-damning oath that Bassanio will remain true. Thus, Portia can count on the integrity of Bassanio through the risk Antonio has taken upon himself in her husband's name.

In comparison with this, the role of Jessica and Lorenzo clashes as the polar opposite. Their act of marriage comes about through a surreptitious escape into the night. Thus they flee community. Furthermore, when we see them again in Act 5, they are out alone under the bright stars. Their presence as a contrast in the story draws the reader's attention to the nature of contractual bonds in marriage. It prompts the reader to inquire into the nature of marriage.