To understand early modern conflict over the question of diversity we need a more nuanced history of philosophy, alert to the traditions of argument and counter-argument available to participants in the debate. With this we may begin to identify the contours and fault-lines that separated opponents addressing fundamental problems of human variation. The third Earl of Shaftesbury and Francis Hutcheson, as we will see in later chapters, disputed Locke's conclusions even as he set the terms of the argument. The difficulty, as they saw it, was not Locke's politics or his position on toleration, which they admired, but rather his willingness in the Essay to cite profound human differences in moral and religious matters without explaining them satisfactorily and restoring the normative force of nature. Where they sought uniformity, under the influence of Stoic teaching, he was only willing to acknowledge incommensurable customs, manners, and beliefs.

Locke's readiness to introduce this material owed something to the method of natural history, as I argued in the previous chapter. His accumulation of testimony on customs and manners treated human nature as something to be understood inductively, rather than through pre-assigned assumptions about essences. The modern, up-to-date, references to travel accounts he provided placed him in the company of naturalists who showed a similar enthusiasm for travel as a source of testimony and evidence. But Locke's argumentative strategy, as it emerged in the Essay, had another pedigree which we need to appreciate: the sceptical tradition.