  The mistake that the skeptic makes, according to Reid, is to deny the truth of something that is demanded by our constitutions. To perceive an object as possessing a particular property is to have a conception of the object delivered by one's constitution. What makes us convinced of the accuracy of the conceptions of objects involved in perception is that they arise from our constitutions. But, asks Reid here, why do we find skeptical arguments so compelling? Why would someone sincerely accept the radical skeptical conclusions following from Descartes's hypothesis of the evil demon?