The Cogito (n.) is only able to be performed if the one saying 'I think therefore I am' is qualified in a certain way by society as someone who is not mad.
The Cogito (n.) is not a discovery but a ceaseless task constantly to be undertaken afresh, a task of managing the distance that both separates and links thought-conscious-of-itself and whatever, within thought, is rooted in non-thought.
The Cogito (n.) in its modern form asks: what must I be, I who think and am my thought, in order to be what I do not think, and for my thought to be what I am not?
The Cogito (n.) in Descartes made error, dreams and madness harmless by showing them to be thought; the modern cogito instead prizes the distance between self-conscious thought and whatever in thought is rooted in non-thought — a ceaseless task, not an evident truth.
The Cogito (n.) in Descartes passed from 'I think' to 'I am' in the light of evidence because Classical discourse existed to link representation and being; no question about the mode of being of the thinker could be asked while that discourse lasted.
The Cogito (n.) in its modern form does not lead from 'I think' to 'I am': can I say I am this language I speak, this labour that eludes me before I begin it, this life that poses me for a moment on its crest? I am and I am not all this.