> This does not commit me to the view that running is fundamental to s's personhood.

That is not Descartes conclusion or my conclusion.

To Descartes, the person as experienced in a priori thought has a special primacy over all other existing things. While "s" may be doubted due to its a posteriori nature, the self is fundamentally undoubtable in its existence, hence "I think therefore I am".

To Descartes, the existence of a priori thought is the building block of all logic and personhood.