| Quote #4
The casket contest for Portia's hand in marriage is a pretty risky undertaking: if a suitor chooses the wrong casket, he can never pursue marriage (with anybody) again. Here we learn that some of the suitors would rather not play this game. They clearly desired marriage (or they wouldn't have shown up), but it isn't worth the risk. This pretty much automatically disqualifies them from being worthy of marrying Portia. It seems her father was looking for someone who'd be willing to risk everything for the girl.
| Quote #5
This doesn't bode well as a comparison: Brutus's Portia was indeed a noble woman, but Brutus wasn't exactly the greatest husband. In Shakespeare's play Julius Caesar, Portia dies a fairly arbitrary death, and Brutus shakes it off pretty easily. Hmm.
| Quote #6
It seems rather arbitrary and harsh that the condition to try for Portia's hand is that losers can never seek marriage again. Still, it holds up marriage as a really serious affair and helps separate the men from the boys in terms of who's really willing to sacrifice for the chance to marry Portia.