Conversation so far:
When did Frederick Douglass become an abolitionist?
Frederick Douglass joined several organizations in New Bedford, and regularly attended abolitionist meetings after moving with his wife to New Bedford, Massachusetts in 1838.
What did Frederick Douglass do as an abolitionist?
In his time, Frederick Douglass was described by abolitionists as a living counter-example to slaveholders' arguments that slaves lacked the intellectual capacity to function as independent American citizens.
Who did Frederick Douglass give the speech to after meeting William Lloyd Garrison?
At a Bristol Anti-Slavery Society meeting, Frederick Douglass was unexpectedly invited to speak.
How was Frederick Douglass' speech received at the Bristol Anti-Slavey Society?
After telling his story, Frederick Douglass was encouraged to become an anti-slavery lecturer.
did Frederick Douglass's speech to the Bristol Anti-Slavery Society receive any praise?
When did Frederick Douglass become a preacher?
Frederick Douglass became a licensed preacher in 1839.
Where did Frederick Douglass preach after becoming licensed in 1839?
In 1840, Frederick Douglass delivered a speech in Elmira, New York, then a station on the Underground Railroad.

Question: what did he preach?
Self-contained rewrite: What topics did Frederick Douglass preach about?