In Chapter 5, Equiano details a litany of real examples he has encountered of enslavers' cruelty. He uses a metaphor to argue that slavery is bad not only for enslaved people, but also for enslavers:
For I will not suppose that the dealers in slaves are born worse than other men. No; it is the fatality of this mistaken avarice, that it corrupts the milk of human kindness and turns it into gall.
He compares human kindness to milk that turns into "gall" when it comes into contact with the "mistaken avarice" of slavery. Equiano is playing with the multiple meanings of "gall." It can refer to bitterness or sourness, so it captures the idea of milk that has gone off. Sometimes it is another name for poison, which has an even darker and more dangerous connotation than sour milk. Additionally, it can refer pejoratively to behavior that is especially daring or out-of-line. Equiano paints a picture of enslavers who were once as sweet and nurturing as fresh milk, but whose natures curdled when they learned that they could make money by enslaving people. It is not that enslavers are innately predisposed to "gall," but rather that slavery turns their natures as dangerous as spoiled food. Equiano thus pathologizes the behavior of enslaving people while also arguing that enslavers have been taken in by an evil institution.
Equiano is using a common abolitionist tactic here. Today, we usually take the abolition of slavery as a foregone conclusion. In the 18th century, it was still a fairly fringe, radical idea. Abolitionists needed to draw as many supporters to their side as possible, especially supporters with money and influence. Enslaved people already knew that slavery was a terrible, inhumane institution. It was the people who were benefiting economically from slavery that abolitionists most needed to convince. Equiano and others often aimed to do exactly this by showing enslavers that they would personally benefit from abolition.
A motif in the book is the sudden interjection of pithy verse into Equiano's narration. In Chapter 11, when Equiano describes how he prevented Captain Baker from lighting a barrel of gunpowder on fire, he uses a verse metaphor to sermonize about the Captain's anger:
I found Him [God] a present help in the time of need, and the Captain’s fury began to subside as the night approached; but I found
That he, who cannot stem his anger’s tide,
Doth a wild horse, without a bridle, ride.
Captain Baker has a temper, and Equiano is used to having it inappropriately directed toward him. In this scene, Baker has been so angry and out of control that he has been trying for over an hour to blow up both himself and Equiano. Equiano describes being on the verge of killing Baker, but prayer helps him remain composed until Baker finally calms down. Equiano uses verse to compare the angry Captain to someone riding a wild horse with no bridle. The Captain, he suggests, has been "riding" anger that refuses to be tamed.
This verse metaphor allows Equiano to efficiently convey a complex point. He separates Baker himself from his anger. Baker, in fact, has been trying to deal with his anger, but the anger itself is bucking him all over the place. Without a bridle to guide the horse (or a tool to tame the anger) Baker has very nearly been destroyed by his wild anger, and destroyed Equiano in the process. Equiano, on the other hand, has been able to ride his own heightened emotions because he has the tool of prayer. While it is not entirely Baker's fault that he could not get his anger under control in this situation, Equiano suggests that he should equip himself with prayer or other tools for managing his emotions. Equiano's verse often contains similar bits of wisdom that he has cultivated throughout his life.
