Answer: descartes

AnswerCrossword Clue
DESCARTES

"Cogito ergo sum" philosopher

DESCARTES

"Cogito ergo sum" source

DESCARTES

His motto: Cogito, ergo sum.

DESCARTES
Great mathematician.
DESCARTES
French philosopher.
DESCARTESHe fathered analytical geometry
DESCARTESCartesians are his followers
DESCARTES'I think, therefore I am' thinker