The anti-slavery creed

In the speech, “What to the Slave is the Fourth of July,” Douglass asserts that “there
is nothing to be argued in the anti-slavery creed” because the fact that the slave is a man
“is conceded already” (1238). Detail two of the points that he makes to support his
assertion. In other words in what ways has the enslaved person’s manhood/ humanity
already been conceded?