Certainty and Speaking

According to a widely-accepted interpretation of it, Descartes' procedure at the outset of the Meditations consists in two main phases--1. A withdrawal from the world to a personal I; and 2. The discovery of that I in a mental operation.  However, #1 is subject to the alternative analysis that the transition begins in personal sense-experience, and ends at an impersonal, universally common, I.  Furthermore, the purported 'mental' operation cited in #2, i. e. I think, is derived from the process of Doubting, which, as Descartes might have difficulty disputing, is based on the ability to say 'No'.  In other words, according to that challenge, Doubting presupposes Speaking, and, similarly, 'I think' is, more accurately, 'I affirm', as is evinced by the construction 'I think that P'.  So, on the alternative interpretation of Descartes' procedure, his achievement of Certainty is the discovery of his ability to Speak.