Rene Descartes:

I confess that I have never found in my experience that anything which I once clearly understood could afterwards be called into doubt by me.

— Rene Descartes Early Modern

Cogito ergo sum

Letter to Mersenne

1630 (approximate)

Verification

Unverifiable

Found in 1 providers: grok

Cross Reference

1 source

"The light of natural reason is not less certain than that of revelation."

"I have never had any experience that was not accompanied by some thought."

"It is not enough to walk with great strides, it is necessary to walk in the right road."

"The nature of the mind is entirely distinct from that of the body."

"It is not enough to apply our mind to things, but we must also apply it to ourselves."