When Shylock appears before the Duke, his initial mood can best be described as vengeful. He takes an uncompromising stance and wishes to exact his revenge. Even when the Duke asks him to be merciful and kind to the unfortunate Antonio, he refuses to budge and states, in part:
I have possess'd your grace of what I purpose;
And by our holy Sabbath have I sworn
To have the due and forfeit of my bond: ...
He continues to state that he does not wish to answer to the Duke's appeal and his query as to why he so much wants a pound of Antonio's flesh since it would be worthless to him. He then suggests that it is to suit his disposition and for no other reason. He then provides a variety of examples of what one could possibly dislike or not without any substantial reason but that it cannot be tolerated. He asks a rhetorical question about whether one should be embarrassed even further in removing such an irritation after having been humiliated by it already.
Shylock is suggesting that he finds Antonio an irritation but states:
... So can I give no reason, nor I will not,
More than a lodged hate and a certain loathing
I bear Antonio, that I follow thus
A losing suit against him.
He refuses to explain exactly why he seeks a pound of Antonio's flesh, but for the fact that he has a deep hate for him and finds him repugnant. It is for this reason that he seeks redress from the court since Antonio has forfeited on the bond.
He retains this obstinate attitude practically throughout the trial. Shylock demands what he believes is justice, for he tells the Duke:
The pound of flesh, which I demand of him,
Is dearly bought; 'tis mine and I will have it.
If you deny me, fie upon your law!
There is no force in the decrees of Venice.
I stand for judgment: answer; shall I have it?
He says this even when he is offered twice the value of the bond. He refuses to give in and extend mercy and insists that he will have his way. If not, then Venetian law is worthless and contemptible and, therefore, has no authority. He insists on having a ruling made and asks whether he will be given one.
The Duke is clearly irritated by Shylock's attitude and states that he has the authority to dismiss the court and thus not pass judgement unless a learned doctor of laws, Bellario, arrives to address the court. It so happens that Portia, disguised as the famed doctor's emissary, comes to address the court on the matter.
When Portia, after asking Shylock to show mercy, which he obviously refuses to do, informs the court that he is within his rights to make his claim and that Antonio should prepare his bosom so that Shylock may cut out his pound of flesh, the Jew is mightily pleased. He calls her all kinds of flattering names and believes that he has succeeded in his petition.
When Portia then makes Shylock aware of the more particular requirements of the law, that he should not shed one drop of Antonio's blood in the cutting of his flesh since he would then have to forfeit all he has to the state, he backs off and requests that he would then rather have thrice the amount owed to him and let Antonio go.
Portia, though, has another ace up her sleeve and informs him that in terms of Venetian law he may remove the flesh he wants but that its weight should not be an inkling more or less than a pound. If it should, he would be executed and all his goods forfeited to the state. Shylock then asks for only the money that he is owed but Portia tells him that he can have only what he asked for. Surely, Shylock has a dilemma.
It is at this point that Portia plays her trump card. She informs the now miserable Shylock that in terms of Venetian law, if any foreigner directly or indirectly seeks to harm a citizen of Venice, he shall forfeit half his estate to the target of his malice and the other half to the state. A decision about his fate would be determined by the Duke.
Since Shylock has sought to harm Antonio, he is told that he should beg the Duke for mercy. The Duke then decides that Shylock should give half his estate to Antonio and the other half to the state. Shylock is deeply distressed and asks that his life rather be taken since he will not be able to survive without having the means by which he lives.
Antonio finally beseeches the court that Shylock's property should be divided and that half be given to Lorenzo, Shylock's son-in-law and the other half willed to both Lorenzo and Jessica upon his death. Shylock must also become a Christian.
One cannot sympathize with Shylock since he had brought all this upon himself. If he had not been so overwhelmed by hatred, revenge, and recalcitrance, none of what had befallen him would have happened. All that he had to do was to be merciful -- something he rejected with contempt.