Convince me that one man may rightfully make another man his slave, and I will no longer subscribe to the Declaration of Independence.
I do not know how to espouse freedom and slavery together. I do not know how to worship God and Mammon at the same time. If other men choose to go upon all fours, I choose to stand erect, as God designed every man to stand.
In the speech William uses logos by talking about what the Declaration of Independence says. He uses the Declaration of Independence as data. He says "Convince me that liberty is not the inalienable birthright of every human being."