Deceit
Solomon Northup's getting sold into slavery in the first place is based on a bald-faced lie, a choreographed deception that is shockingly revealed. The two men who hire Solomon on the pretense that he will play violin in a circus performance end up drugging his drink and selling him into slavery. After having fallen asleep at a lavish dinner, he awakes in chains. He is being called a different name, and has been stripped of his identification papers. This initial deceit sets the stage for the entire film, and represents the ways that a black man cannot trust a white man, for fear that such a horrifying fall from grace might occur.
Throughout the film, Solomon must weigh whom to trust, as his trust has been so broken by the deceit of the men who sold him into slavery to begin with.
Violence
Violence, in all its forms, is also a major theme in the film. Solomon witnesses and experiences many different kinds of violence throughout his time as a slave. He sees women getting raped and men getting killed when they stand up for the women. Tibeats hangs him from a tree after he exhibits his intellect in front of him on Ford's plantation.
Then, on Epps' plantation, violence proves to be a general ethic, a way of life. Epps is a fundamentally reckless and violent man, often taking out his insecurities and resentments on his slaves, whether he is raping or abusing Patsy, or forcing his slaves to dance for him in the middle of the night. His wife shares his violent streak, slashing Patsey's face and throwing a bottle at her while she dances. The final and most devastating act of violence occurs when Epps punishes Patsey for visiting Shaw's plantation in search of soap. He strips her and ties her to a tree, before ordering Solomon to whip her, and then whipping her himself. The scene is devastating, shocking, and horrific in its depiction of violence, and the ways that the white slaveowner's violence ripples outward and infects everyone in his charge.
Power & Entitlement
The reason Epps feels entitled to commit such horrible acts of violence, and indeed, the reason that any of the white characters feel entitled to commit any injustices against the black characters is because it gives them a sense of power. Mistress Epps continually chides her husband about not wielding enough power with his slaves, emasculating him so as to encourage him to exert more power over them. He himself is committed to the institution of slavery because he believes he is entitled to treat his slaves however he chooses, as they are his property. Arguably, his sexual relationship with Patsey has more to do with exerting his power over her than it does with attraction. Power, and feeling entitled to, power is a major theme in the film, and it defines most of the white characters' attitudes towards their status in society and their sway over the fates of the black slaves in their charge.
Survival
Solomon's main priority is survival, and he must learn—sometimes the hard way—how to survive in scenarios that seem stacked against him. At first, on Ford's plantation, he tries to use his education and wherewithal to excel, but this only makes life harder, when a white worker feels threatened by his superior intellect. After that, it is his motive to survive in whatever way he can.
At one point, Solomon speaks about survival to another slave, Eliza, who has been separated from her children. She cries openly about her loss, and the Fords are beginning to think she's becoming more of an annoyance than anything. When Solomon warns her about this, she insists that she must express her grief and tells him that he is compromising his dignity by simply figuring out how to survive. Each of the slaves has a different attitude towards survival and what it takes.
Mercy
Patsey does what she must to survive for much of the film, but is beaten down by the abuse she suffers at the Epps' plantation. At one point, she begs Solomon to take her to the river and strangle her so that she can finally find some peace. She suggests that because God will show her no mercy, she needs to find someone who will. In her mind, life as a slave is so violent and undignified that the only way to find mercy and grace would be to die and be relieved from her pain. Solomon protests, suggesting that he cannot kill someone, but Patsey insists, "God is merciful, and He forgive merciful acts. Won't be no hell for you."
Freedom
The film follows the story of a man who was once free who finds himself as a slave under extraordinary circumstances. Through this story, we see the particular pain of Solomon having known what it was like to live as a free man before getting sold, and thus always having something to compare his miserable life of enslavement to. He dreams of freedom, wondering when and if he will ever experience it again.
When he meets Bass, the Northerner who has a critique of slavery, the two men discuss freedom. Bass empathizes with Solomon's plight, recognizing that he himself has the freedom to walk off the plantation whenever he chooses. It is this understanding of how freedom is essential to a worthwhile life that motivates Bass to help Solomon escape enslavement and return to his home.
Music
Solomon Northup is a violinist, and when we see his life in Saratoga, he plays music at various functions, living happily as an artist in his community. When he gets sold into slavery, this identity is completely taken away from him, but Ford does buy him a violin while he is working on his plantation. Solomon plays for pleasure there. Then, at Epps' plantation, he plays the violin during Epps' perverse dances, a time when he must use his musical abilities in horrific contexts. Towards the end of the film, we see Solomon destroying his violin, a representation of his broken spirit. Music stays with Solomon, an important part of his identity, but it also changes in meaning in different contexts; through this we see that nothing is protected against the hardship of slavery.
