Date: 1641

"I am not that structure of limbs which is called a human body. I am not even some thin vapour which permeates the limbs - a wind, fire, air, breath, or whatever I depict in my imagination; for these are things which I have supposed to be nothing."

— Descartes, René (1596-1650)

Date: 1641

"And whenever my preconceived belief in the supreme power of God comes to mind, I cannot but admit that it would be easy for him, if he so desired, to bring it about that I go wrong even in those matters which I think I see utterly clearly with my mind's eye."

— Descartes, René (1596-1650)

Date: 1644, 1647

A 'clear' perception is analogous to an object "present to the eye's gaze" that "stimulates it with a sufficient degree of strength and accessibility"

— Descartes, René (1596-1650)