Authority
The imagery of absolute authority is on display in the novel. Since this is the illegitimate family of US President Thomas Jefferson, one naturally considers the ironic presence of power in this situation. This is perhaps the closest that a slave could possible come to influencing American politics, but instead of standing up for his socially unacceptable romance with a slave, Jefferson opts instead to shower his new family with privilege which goes away when he dies. He upholds an authority that invalidates his own family.
Race and slavery
The imagery of race is shown in complicating ways, because on the one hand, racism and slavery are clearly the thematic content of the book, but many of the main characters pass for white, except that their legal paperwork keeps them enslaved. This inversion of expectation has the effect of irony. Considering that white people might be slaves shows the absurd and racist prejudice that undermines American slavery. The fact that one's race determines one's existential value in American slavery is shown to be absurd.
Legitimacy
For the title character, Clotel, or the President's Daughter, legitimacy is the major imagery of life. Her identity is illegitimate, and when she falls in love, their marriage is deemed legally illegitimate. When she has children, they are deemed illegitimate. Her own existence is illegitimate by law, because the literal President of the United States broke the law he symbolically upholds. The question of legitimacy points the reader to the truth, that what was in fact illegitimate about the situation was the absurd toleration of an evil institution like slavery.
Freedom and marriage
Mary's life is defined by struggle toward freedom. She is a survivor of American slavery who escapes and lives a happy, healthy life free from America and American politics. In France, her identity is plainly valid. This is a way of proving through imagery what the family knows all along. By changing the imagery from America to France, the absurdity of American slavery is clarified, because as a freed person, Mary is clearly equal in every way to her peers. The idea that she might be less because her mother were Black is simply racial superstition and hatred.
