Descarte made the fatal conceit of believing that there is anything to question or anyone to question it. Once he included the word 'I', the folly was complete and passed to us as some odd gospel.
Nevermind that it runs entirely contrary to the true Gospel....
Correctly constructed, it would be:
"Thought exists with no one to think it and nothing to be thought of, therefore God exists."
Careful, you're getting close to real truth there.