The correct answer to this open question is the following.
According to Douglass, laws in the south prove that slaves are human beings in those laws passed in the south punish slaves as punish white men.
Douglass used the reference of the laws passed in the southern state of Virginia. In the speech "What the Slave is the 4th of July?, of July 5, 1852, Frederick Douglass addressed the Rochester Ladies' Anti-Slavery Society. In the speech, Douglass referred to the fact that words such as liberty and celebration were not part of the slave's vocabulary, to the contrary.
