When discussing the matters of the law, one must accept what is written in the law books which are accepted by the people or rulers of the country. Laws are written in order to protect people from harm or unfairness. "Justice" is a word that connotes strength and fairness while "Mercy" seems to present itself as a weak idea reserved for victims. Justice is an idea that people call for when they feel they have been treated unfairly and want the law to fix the problems between two factions. Mercy is a gift of forgiveness not truly understood or given easily. Along these lines of thinking enters Shylock who demands justice but is asked to give mercy. Christianity and Judaism also clash in the debate as to what should hold stronger under Antonio's unfortunate circumstances.The irony comes in when a person who thinks that the law is on his side forgets mercy and demands justice. Justice systems would lose the trust of the people if it handed out mercy all of the time. Thus, when Shylock refuses to accept anything other than Antonio's pound of flesh, Portia says, "A pound of that same merchant's flesh is thine;/ The court awards it, and the law doth give it"(IV.i.307-308).
The only way that justice can be satisfied is if payment for any contract is paid. Luckily, Justice doesn't care who pays the debt, only that the contract is fulfilled. This is why Portia gave Bassanio permission to offer 6,000 ducats! She thought that any man would be willing to accept double the contract and release Antonio from the contract. Only if Shylock had dropped the case could the law back away from executing itself.
Sadly, Shylock was blind-sided by a law that he didn't know about which turns the tide against him and forces him into a position of asking for mercy. If Venitian law had not demanded that no blood should be shed, then Shylock would have had his justified way. The only two ways that Justice can be satisfied is if the contract is paid or if the petitioner drops the charges. Justice is blind for equality's sake, but Mercy is subjective and dependant upon the choice of one who would sacrifice something valuable for someone else who is trapped or has nothing of value. Mercy can only overcome Justice when it is freely given by a person's choice. Justice has claim over all who must obey the law.