"I think, therefore I am" means: "The only thing I can be sure of is the existence of my own thoughts, because when I doubt others, I cannot doubt my own thoughts at the same time."

A more authoritative explanation is: "I cannot deny my existence, because when I deny or doubt, I already exist!" Because when I am thinking and doubting, there must be an execution of "thinking" "The "thinker", this "I" as the subject cannot be doubted. This "I" is not the extended physical "I", but the thinker's "I". Therefore, denying one's own existence is self-contradictory.

"I think, therefore I am" can be succinctly understood as: when I use reason to think, I truly gain the value of existence. Reason can break away habits, superstitions and various so-called "established concepts", allowing real thinking to penetrate into one's life. Then, my existence will have real meaning.

Descartes' "I think, therefore I am" is the starting point of Descartes's entire epistemological philosophy and the end point of his "universal doubt". From this point he confirmed the legitimacy of human knowledge.

In other words: Descartes is an idealist, but this cannot be seen from this proposition. "I think, therefore I am" is not an idealist proposition, but the content of pure epistemology. To say that Descartes is an idealist is a conclusion drawn from an overview of his philosophical system, not from this proposition, which is neither materialist nor idealist.