The conflict between the principle of liberty and the fact of slavery is coming gradually to an issue. Slavery has now the power, and falls into convulsions at the approach of freedom. That the fall of slavery is predetermined in the counsels of Omnipotence I cannot doubt; it is a part of the great moral improvement in the condition of man, attested by all the records of history. But the conflict will be terrible, and the progress of improvement perhaps retrograde before its final progress to consummation.

Journal of John Quincy Adams (11 December 1838), Miller, William Lee (1995). Arguing About Slavery. John Quincy Adams and the Great Battle in the United States Congress. Vintage Books. p. 344. ISBN 0-3945-6922-9.