Abstract: Central to Peirce's rejection of the Cartesian obsession with scepticism is the claim that sceptical arguments do not produce real doubt. This chapter provides a detailed examination of the role of doubt in the regulation in inquiry, claiming that states of real doubt involve immediate cognitive evaluations that are manifested in emotional reactions such as epistemic anxiety. Many of our most important epistemic evaluations reflect habitual standards of evaluation that are not explicitly articulated and that are expressed in emotional evaluations.

Keywords: Cartesianism, doubt, emotions, evaluation, habits, real doubt, scepticism,