Descartes found it impossible to doubt his own existence. The reason for this was that he felt that thoughts had to come from himself.
Short answer: Descartes' doubt was like WWI - the doubt to end all doubt. Only by doubting everything could Descartes hope to find anything that was certain (even if the only certainty is that nothing else is certain!).
That he is sentient ie that he thinks.
he believed if you can doubt it, it must not exist.
i am i exist
Descartes found it impossible to doubt his own existence. The reason for this was that he felt that thoughts had to come from himself.
Descartes cannot doubt his own existence, as captured in his famous statement "Cogito, ergo sum" - "I think, therefore I am."
"I think, therefore I am" is the first truth of which Descartes is certain. This statement, known as cogito ergo sum, demonstrates Descartes' method of doubt by acknowledging that even if all his perceptions are false, his ability to doubt and think proves his existence as a thinking being.
Short answer: Descartes' doubt was like WWI - the doubt to end all doubt. Only by doubting everything could Descartes hope to find anything that was certain (even if the only certainty is that nothing else is certain!).
Systematic doubt. Descartes could doubt everything except for one thing - his own existence. Cogito ergo sum - "I think, therefore I am" - became his first principle.
Descartes attempts to doubt everything he believes to be true in order to find a foundational belief that cannot be doubted. He starts by doubting his senses, then his perceptions, and finally even the existence of the external world. Through this method of doubt, he arrives at the conclusion that his own existence as a thinking thing ("I think, therefore I am") is indubitable.
He can not doubt that he thinks, therefore he exists.
In Descartes' Meditations, doubt serves as a tool for philosophical inquiry by challenging and ultimately casting skepticism on the reliability of sense perceptions and beliefs. Through methodical doubt, Descartes aims to uncover indubitable truths and establish a foundation of certain knowledge upon which to build his philosophical system. Doubt, therefore, acts as a catalyst for Descartes' quest for certainty and the establishment of foundational principles in his philosophy.
René Descartes, a French philosopher, created the system of systematic doubt. In his work "Meditations on First Philosophy," Descartes employs the method of doubt to question all his beliefs in order to find a foundation of certainty in knowledge.
That he is sentient ie that he thinks.
Descartes hopes to find out what he can know for certain, without any doubt, about the world and nature.
Descartes' theory of knowledge was to doubt all things and accept as knowledge the things that could not be doubted