How is it that Portia disguised manages to defeat Shylock and why?
Portia, dressed as a man and impersonating a lawyer, manages to save Antonio's life and to disgrace and thwart Shylock by providing a close reading and interpretation of Shylock's written agreement with Antonio. The original document calls for a pound of flesh to be extracted from Antonio by Shylock if a loan is not repaid on time. Just before Shylock is about to make good on this agreement, Portia says "Tarry a little": perhaps she imagines what she will see before her and the anticipated sight of blood causes her to realize she can prevent this public bloodshed. She remarks that the document does not allow for any drop of blood to be shed; and so, since Shylock cannot extract the pound of flesh without shedding blood, he cannot have his revenge on Antonio. Shylock also loses his fortune as a result of Portia's legal arguments.