 Evidentialism of some sort is far and away the dominant ethic of belief among early modern and contemporary philosophers alike. The central principle, as mentioned earlier, is that one ought only to base one's beliefs on relevant evidence (i.e. evidence that bears on the truth of the proposition) that is in one's possession. Many Evidentialists (Locke, Hume, and Clifford, for example) add the condition that the amount of evidence in one's possession must be proportioned to one's degree of belief, and that one should only firmly believe on the basis of “sufficient” evidence (where “sufficient” involves the evidence being strong enough for the belief to count as knowledge if true). Some also add one of the reflective access requirements mentioned above: for instance, that we ought to know (or being a position to know, or justifiably believe, or be justified in believing) that we have evidence for the original belief or even that the amount of evidence we have is sufficient (for a survey of these positions and their critics, see the essays in Dougherty 2011).