What most likely influenced the struggle to end slavery in the United States in the 19th century?

Enlightenment thinkers believed that the human ability to reason makes all people equal. They also believed that, if people are all equal, they should have equal freedoms and rights as citizens. The impact of this idea can be seen in the language of the U.S. Declaration of Independence ("life, liberty, and the pursuit of happiness"). It also helped inspire the abolitionist movement to free African slaves in the United States in the 19th century.