 The certainty/indubitability of interest to Descartes is psychological in character, though not merely psychological – not simply an inexplicable feeling. It has also a distinctively epistemic character, involving a kind of rational insight. During moments of certainty, it is as if my perception is guided by “a great light in the intellect” (Med. 4, AT 7:59, CSM 2:41). This rational illumination empowers me to “see utterly clearly with my mind’s eye”; my feelings of certainty are grounded – indeed, “I see a manifest contradiction” in denying the proposition of which I’m convinced. (Med. 3, AT 7:36, CSM 2:25)