Vulcan wrote:
Cogito ergo sum!
you can doubt everything, but you cannot doubt that you doubt...
No, no, you can doubt that you doubt. Doubt could be a concept that has no meaning or I could be in a state of utter ignorance totally incapable of doubt.
The only thing I can not doubt is that I exist (according to Descartes and other dualists) or that the phenomena I experience exist.