The question is very complex. Shylock asks for "justice" in his demand for the pound of flesh, but Portia (disguised as a lawyer) advises him that mercy is a higher value than justice, and that he should show Antonio mercy. When Shylock refuses, Portia tricks him, telling him he may have only the pound of flesh, no blood, which in effect renders his plea worthless. Thus, Portia holds him to the very strict letter of the law that Shylock asks for: "Thou shalt have justice more than thou desir'st" (4.1.330). She also holds him accountable to another law, that of, as an alien (for Jews were not citizens), threatening the life of an Venetian citizen (4.1.363-370). His punishment, decreed by Antonio, is to convert to Christianity and give up his money (in different ways). To Shakespeare's audience this would be justice (indeed, such a conversion might to that audience save Shylock's soul), but we might think how enormous this sentence is: Shylock loses his religion as well as his livelihood, not to mention his daughter. He has already suffered humiliation for being a Jew, which prompted his behavior to begin with. So, from our point of view, the mitigating circumstances are such that perhaps Antonio could have shown a bit more of the mercy Portia spoke of in her famous speech.