This essay presents an argument, which it calls the Bias Argument, with the dismaying conclusion that (almost) everyone should significantly reduce her confidence in (too many) philosophical beliefs. More precisely, the argument attempts to show that the most precious philosophical beliefs are biased, as the pervasive and permanent disagreement among the leading experts in philosophy cannot be explained by the differences between their evidence bases and competences. After a short introduction, the premises of the Bias Argument are spelled out in (...) the first part. The second part explains why the objections to the Bias Argument are not compelling. Even though the essay does not adopt the conclusion of the Bias Argument, partly because it seems to be self-defeating, the authors know no plausible way to refute its premises. Thus, the primary aim of the essay is to clarify why the aporetic situation of the Bias Argument arises. (shrink)