[cornelis]

Why not sum ergo cogito?

Descartes admitted the idea of infinity as real. Hobbes wouldn't. In the Meditations, Descartes has reasons: his own finitude implied divine infinity.

[katana]

If it weren't for the fact that there are lots of people who demonstrably are but who nonetheless show no signs of actual thought your reversal of "I think therefore I am" to "I am therefore I think" (sum ergo cogito) might have more merit.