Pathos

Yeah, this one's gut wrenching.

Rhetoric that relies on pathos works by creating an emotional response in the listener. In "The Church and Prejudice," Douglass accomplishes this by co-opting the religious language of the Second Great Awakening, which relied largely on revival preaching designed to provoke emotional religious conversions. Check it out:

Now it so happened that next to her sat a young lady who had been converted at the same time, baptized in the same water, and put her trust in the same blessed Saviour; yet when the cup containing the precious blood which had been shed for all, came to her, she rose in disdain, and walked out of the church. Such was the religion she had experienced! (12-13)

Douglass tries to get listeners to have the same type of emotional response to slavery that they might have for religion by showing how bad slavery is and how hypocritical slave owners are:

I used to attend a Methodist church, in which my master was a class leader; he would talk most sanctimoniously about the dear Redeemer, who was sent "to preach deliverance to the captives, and set at liberty them that are bruised" —he could pray at morning, pray at noon, and pray at night; yet he could lash up my poor cousin by his two thumbs, and inflict stripes and blows upon his bare back, till the blood streamed to the ground! all the time quoting scripture, for his authority, and appealing to that passage of the Holy Bible which says, "He that knoweth his master's will, and doeth it not, shall be beaten with many stripes!" Such was the amount of this good Methodist's piety. (41-43)

Those very personal anecdotes were a direct appeal to the sympathies of his readers. If that doesn't get you all riled up to annihilate slavery, we don't know what will.