Writing, Cogito, Certainty

As has been previously discussed here, the scenario that Descartes describes in the Meditations is not quite as he presents it, i. e. he is plainly at a desk writing, not conducting a thought-experiment while sitting in front of a fire.  Still, it might be argued that the discrepancy is extrinsic to the described procedure and its results.  However, on the other hand, the non-coincidence is perhaps fatal to the entire project.  For, the pivotal proposition in the exercise is 'I cannot doubt that I am doubting', on the grounds that 'One cannot simultaneously doubt and not doubt'.  So, the presumption of that simultaneity is essential to procedure.  But, that Descartes is merely reporting it only amplifies what critics since Kant have argued--that doubting that one doubts consists in two, successive, acts.  In other words, in the writing of the Meditations, Descartes cannot attribute Certainty to any Cogito that he is reporting, unless he somehow identifies it with that process of describing.