I was thinking about Descartes’ classic example of doubt. His attempts to identify the most secure form of knowledge lead him to his own consciousness as the unassailable ground of knowing. I agree with his assessment though I think it misses an essential point, namely, that there is an existential as well as a epistemic puzzle behind the normal lack of doubt about our own existence or consciousness. Of course this is not a reason to think that consciousness and existence are domains outside the scope of doubt, but it does suggest that the lack of doubt reveals an essential aspect of how we know our own existence. I think that the essence of how we experience and know ourselves is tangential to the kind doubt that concerns Descartes, who is after certainty.