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)

Date: w. 1628, published in 1684, 1701

"The writers displayed many geometrical truths before my very eyes, as it were, and derived them by means of logical arguments"

— Descartes, René (1596-1650)

Date: w. 1628, published in 1684, 1701

"We can best learn how mental intuition is to be employed by comparing it with ordinary vision."

— Descartes, René (1596-1650)

Date: w. 1628, published in 1684, 1701

"Moreover, as we said, we should not contemplate, in one and the same visual or mental gaze, more than two of the innumerable different dimensions which it is possible to depict in the imagination."

— Descartes, René (1596-1650)