Freedom and autonomy
Calhoun is no fool. Just because he isn't technically a slave, that doesn't mean he is autonomous, enfranchised, and free. Quite the contrary. When Isadora offers to pay his debts, that's not different than a slave trade, because he only owes money to Zeringue because Zeringue is a racist who exploits black people for profit. Proof of this is found in the end of the novel when Calhoun has documents implicating Zeringue in the illegal slave trade. So when Isadora offers money in order to blackmail Calhoun into marriage, she's attempting to purchase him. Calhoun's first taste of real autonomy comes from his wise voice on the boat, helping to make the boat last until help can arrive (because without the crew and captain, they are in dire trouble). His freedom is the result of his clarity and balance.
Non-violence and cooperation
When Calhoun stops the African tribesmen from destroying the boat, that is a little like the superego managing the ego and id. The ego and id want what will appease their feelings and emotions, like the Africans want vengeance for being kidnapped and enslaved (rightly so). There's only one problem; if they get what they want, the boat will literally sink. Calhoun is the voice of reason that says that only through non-violence and cooperation can any of them survive at all. He encourages them to do what is best for themselves, instead of what will feel best.
Dilemma and conflict
Without a doubt this novel features conflict and dilemma at its core. For instance, the opening of the book shows a "freed" slave, which is a technical term that sounds like it means more than it means. In reality, Calhoun is free from slavery, but because of the never-ending dilemmas of his disenfranchisement, it's easy for him to make decisions. Basically, Calhoun is a character who is shaped by making the most out of bad situations.
