Thomas Clarkson,
Thoughts on the Necessity of Improving the Condition of the Slaves in the British Colonies
“ What makes an English labourer do more work in the day than a slave, but the stimulus arising from the knowledge, that what he earns is for himself and not for another? What, again, makes an English labourer do much more work by the piece than by the day, but the stimulus arising from the knowledge that he may gain more by the former than by the latter mode of work? Just so is the West Indian slave situated, when he is working for himself, that is, when he knows that what he earns is for his own use. ”
