Read the excerpt from Thoughts and Sentiments.

It is therefore manifest, that something else ought yet to be done; and what is required, is evidently the incumbent duty of all men of enlightened understanding, and of every man that has any claim or affinity to the name of Christian, that the base treatment which the African Slaves undergo, ought to be abolished; and it is moreover evident, that the whole, or any part of that iniquitous traffic of slavery, can no where, or in any degree, be admitted, but among those who must eventually resign their own claim to any degree of sensibility and humanity, for that of barbarians.