Answer:
Rene Descartes
Explanation:
Rene Descartes (31 March 1596 – 11 February 1650) was a French philosopher, scientist, and mathematician.
Descartes determined a single first principle: I think.
In Discourse on the Method and Principles of Philosoph is explained like this : "Thought cannot be separated from me, therefore, I exist".
This is known as cogito ergo sum (in English: "I think, therefore I am").
Descartes concluded that, if he doubted, then, something or someone must be doing the doubting, therefore the fact that he doubted proved his existence.
