This PhD thesis conducts a critical discourse analysis of 12 British pro- and anti-slavery texts from the years of 1784 to 1825. The focus is on understanding the image of Africans in the British debate on the slave trade and slavery by looking at a corpus of argumentative texts. On a methodological level, my analysis is driven by critical discourse analysis in the tradition of Siegfried Jäger, by post-colonial concepts and, on a more practical level, by computer-based text analysis making use of methods from corpus linguistics and qualitative text analysis (MaxQda). In order to arrive at a comprehensive appreciation of the image of Africans the present work analyses texts as fragments of larger discourses and links argumentative strategies and historical references to larger traditions of thoughts such as European humanism and the Enlightenment. The basic premise of this thesis is that, at the threshold from the early to the late modern period, the distinct image of Africans as slaves was instrumental of universalising a Eurocentric concept of capitalist wage labour both at the colonial centres and margins. By portraying African slaves as suffering wretches, especially anti-slavery texts created colonial others in an indistinct zone between inclusion and exclusion from humanity. These mimetic Others could subsequently become the objects of a discourse of colonial reform and ‘betterment.