In The Merchant of Venice, what is the importance of the trial scene and the role played by Portia in the scene?

Antonio’s trial is the climax of the play: having entered into a usury agreement with Shylock on behalf of Bassanio, which he was unable to repay, Antonio has been imprisoned. By the terms of the bond, Shylock can claim a pound of Antonio’s flesh upon forfeiture. Shylock intends to claim his heart, thereby killing Antonio.

 

Portia and her serving woman, Nerissa, disguise themselves as men to intervene in the trial. Portia becomes Balthasar, a doctor of law, and argues that Shylock ought to have mercy for Antonio. Her famous speech begins,

The quality of mercy is not strain'd,

It droppeth, as the gentle rain from heaven

Upon the place beneath: it is twice bless'd

She goes on to extol the virtues of mercy: that it displays power better than a crown ever could, that is is “an attribute to God himself,” that salvation cannot come from justice but only from mercy. In doing so, of course, she extols Christian values, which alienates Shylock as a Jew. However, she rules in favor of Shylock: the bond is forfeit, and therefore Shylock might claim his pound of flesh.

Why, this bond is forfeit;

And lawfully by this the Jew may claim

A pound of flesh, to be by him cut off

Nearest the merchant's heart.—Be merciful;

Take thrice thy money; bid me tear the bond.

But while she concedes that Shylock is owed his pound of flesh, by the terms of the bond no blood has been allotted with it. Therefore, Shylock cannot carve out his pound of flesh. Adding insult to injury, she rules that:

If it be proved against an alien

That by direct or indirect attempts

He seek the life of any citizen,

The party 'gainst the which he doth contrive,

Shall seize one half his goods; the other half

Comes to the privy coffer of the state;

And the offender's life lies in the mercy

Of the duke only, 'gainst all other voice.

Thus, Shylock has fallen: from possessing the power to legally take his enemy’s life to having his fortune confiscated and half given to that same enemy. Portia denies Shylock the same mercy that she had urged him to act upon, hypocritically; insult is added to injury when Antonio allows Shylock to keep half his fortune if he names Lorenzo as his heir and converts to Christianity. Shylock is humiliated and degraded, claiming that:

You take my house when you do take the prop

That doth sustain my house; you take my life,

When you do take the means whereby I live.

The trial scene serves many purposes: one of the main storylines comes to fruition as Shylock receives his downfall; Portia proves herself as capable as any man; and Antonio is relieved of the bond. Portia’s role is pivotal in this scene: without her intervention, Antonio would have died. In saving Antonio, Portia's character is fleshed out: she has gone from a woman trapped by her father's will to a woman more capable than any man present in the courtroom. At the same time, she is revealed to be hypocritical in her attitudes toward Shylock: she urges him to be merciful yet is unmerciful herself.