Professor Hung Wai-Shun's contribution to the Hong Kong PEACE conference is titled Perception and Self-Awareness in Merleau-Ponty: The Problem of the Tacit Cogito in the Phenomenology of Perception (pdf). Here is the absract:
If the legacy of Descartes is his idea of consciousness as a realm of interiority, the contributions of many twentieth-century philosophers consist precisely in their efforts to criticize this Cartesian notion of self. Among these efforts, Merleau-Ponty's Phenomenology of Perception occupies an ambiguous position. While its analysis of being-in-the-world as bodily insertion, of expression as incarnation of sense, and of the opaqueness of our inner life challenges the idea of consciousness as a realm of transparency and self-presence, its notion of a tacit cogito seems to remain a notion of self-presence. This essay attempts to understand Merleau-Ponty's concerns behind the notion of tacit cogito, and suggests that the notion is required in order to account for the self-awareness of every experience. Referring to Merleau-Ponty's self-criticism in The Visible and the Invisible, this essay suggests that the difficulties surrounding this notion come from both its conception of the pre-reflective relation of the self to itself as a kind of "proto-reflection" and its conception of the relation between reflection and the pre-reflective in terms of negativity. However, in the analysis of bodily self-awareness of the Phenomenology we can already find the gems of a notion of self-awareness that could avoid the pitfalls of the tacit cogito, and the essay concludes with a brief discussion of how this line of thought is picked up and developed in Merleau-Ponty's later work.
Though I would urge you to read Hung's paper in its entirity, I will say off the bat that I don't believe that the later train of Merleau-Ponty's thought as presented by Hung actually does avoid the pitfalls of the tacit cogito. I think this has to do with Merleau-Ponty's conviction that consciousness essentially has to do with language. So what is the tacit cogito? The tacit cogito is from the gitgo an impossibility. Starting with the notion that "[a]ll thought of something is at the same time self-consciousness" (Phenomenology of Percepetion, p. 371), Merleau-Ponty designates one's conscious presence to oneself as the tacit cogito, which he says is "no less than existence." But, he says, "[t]he tacit cogito is a cogito only when it has found expression for itself" (p. 404). Does this mean that the cogito is destined for language? I think that is what Merleau-Ponty is getting at, and, thus, I think this but makes his existential phenomenology a humanism. When Merleau-Ponty says "existence" or "life," as in "this ambiguous life" of the truly transcendental (pp. 364-365), he is talking about human existence, about human life. That self-awareness has been observed in dolphins, chimpanzees and elephants, or that semovience might point to a kind of self-awareness broadly shared within the Kingdom Animalia, these facts have nothing to do with the tacit cogito, nor with any kind of bodily awareness that the later Merleau-Ponty riffs on, because these instances of self-awareness are in no way tied to language. We could of course broaden our understanding of language to account for the reflective attitudes of our fellow animals. We might then need another idea of language or signification to account for what humans do. Or, if we want to insist on a single definition of language and a single definition of life, we could say that what Merleau-Ponty identifies as the tacit cogito really does point to something originary, and isn't necessarily destined for language.