The Merchant of Venice reveals a contrast between value systems, expected norms and desired outcomes.
Portia is an independent young woman, a fact that obviously did not escape her father as he attempted - even after his death- to place some restrictions on her. "so is the will of a living daughter curbed by the will of a dead father" (I.ii.24-25).
Portia's father knew that her wealth could be a stumbling block - "The world is still deceiv'd with ornament," (III.ii.74) - but was confident enough of his daughter and her superior intelligence in assigning this requirement in his will.
Having an intelligent daughter, Portia's father must have known she would "manage" his plan and still get the best out of it. She can be petulant so must prove her resourcefulness in "persuading" Bassanio, to pick the right chest. Bassanio may have ,initially, wanted to marry her due to her wealth but it is Portia's clever manipulating of him, because he is her choice, that ensures the desired conclusion.
It is Portia's intelligence that gives her the capacity to look beyond face value and find real worth. She is the one who, ultimately, saves the day and ensures the best outcome through her display of mercy and compassion - "It blesseth him that gives and him that takes (IV.i.188).
Portia shows her cunning when she appears to side with Shylock - in the interests of justice - but uses a loophole to prevent him from obtaining his "pound of flesh."
There are contentious moments when Portia does not behave as the virtuous person that she is but that adds depth to her character. Her almost lack of mercy after her obvious display of such and her frivolous game she plays with Bassanio over the wedding ring.
Portia is able to couple her intelligence with reason and an acceptance of the norms of her society, knowing that she can only be of benefit to Antonio if she dresses as a man and becomes Balthazar the lawyer.
Just as she was able to rationalize and then fulfill - even though she did not like it - her father's wishes she is able to justify her actions in everyone's best interests. Portia's honorable stance and compassionate nature are only useful due to her intelligence - her capacity to use them wisely .