 Third, the certainty of the cogito depends on being formulated in terms of cogitatio – i.e., my thinking, or awareness/consciousness more generally. Any mode of thinking is sufficient, including doubting, affirming, denying, willing, understanding, imagining, and so on (cf. Med. 2, AT 7:28). My bodily activities, however, are insufficient. For instance, it’s no good to reason that “I exist, since I am walking,” because methodical doubt calls into question the existence of my legs. Maybe I’m just dreaming that I have legs. A simple revision, such as “I exist, since it seems I’m walking,” restores the anti-sceptical potency (cf. Replies 5, AT 7:352; Prin. 1:9).