Barbaras offers a critique of Merleau-Ponty's concept of existence, first as it appears in The Structure of Behavior, then in Phenomenology of Perception. I need to quote at length before commenting on Barbaras' criticisms.
. . .Merleau-Ponty must show in a descending movement that if the notion of form grounds a critique of naturalism, it allows us just as much, and for the same reasons, to call intellectualism into question. The meaningful relation of the organism to its environment is still a relation to a reality, to a transcendence, and is not therefore based on a consciousness transparent to itself; it is not based on an act of knowledge. The study of behavior reveals what Merleau-Ponty calls an existence, a being-in-the-world, a tacit relation to a presence rather than a possession of something in a representation. The Structure of Behavior therefore concludes: "The natural 'thing,' the organism, the behaviors of others and my own behavior exist not only by their sense; but this sense which springs forth in them is not yet a Kantian object; the intentional life which constitutes them is not yet a representation; and the 'understanding' which gives access to them is not yet an intellection" (SC 241/225).
(The Being of the Phenomenon (hereafter Being), pp. 4-5, my bold)
Let's push aside the question of whether my philodendron relates to a transcendence (whatever that means) in the same way as organism that are typically thought to behave, which happens to coincide with the class of organisms that typically display motility, such the amoeba, the anole lizard or the elephant who sees itself in mirrors, and also the question of whether organisms ever meaningfully relate to irrealities, or relate without meaning (or form)we are after all not really doing biology at this juncture, though we are on the verge of Barbaras' cosmobiologyso we can focus on the idea of consciousness which Barbaras seems to believe ought to have been jettisoned early on in the development of Merleau-Ponty's phenomenology. Consciousnesses transparent to themselves are not the only kind of consciousnesses, and transparency is not the only imaginable mode of a reflexive relation of consciousness. (I realize an idea of the cogito is being implicitly criticized, fairly or unfairly; the criticism is itself an idea offered in a specific form and it will be tested.) Furthermore, a preintellectual or prerepresentational intentional life is not completely at odds with knowledge or acts of knowledge. Merleau-Ponty doesn't say as much. Why should he? He proposes another kind of "understanding," but he still conceives of it as understanding, a praktognosis he will go on to say in Phenomenology. In fact we might think that understanding is the inflected form of "understanding," once the latter concept has been established in our thinking, without then really doing away with either or being stuck with some antiquated (and derivative, ever problematic) notion of existence which witholds more than it emancipates.
Before carrying on let's look at another passage dealing with Merleau-Ponty's concept of existence as presented in Phenomenology. Barbaras notes that the concept of existence is omnipresent in Phenomenology but disappears in later works.
Existence designates the movement by which the body, which is irreducible, as we have seen, to a pure object, gives sense. In fact, "the human body is defined in terms of its property of appropriating, in an indefinite series of discontinuous acts, meaningful kernels which overcome and transfigure its natural abilities" (PHP 226/193). Existence is thus "this open and indefinite power of meaningthat is, simultaneously of grasping and communicating a senseby which man transcends himself toward a new behavior or toward others, or toward his own thought, across his body and his speech" (PHP 226/194). The central intention of Phenomenology of Perception is this power of escape, this sense always already at work, which is not distinguished from its own accomplishment, and which, in this way, cannot be opposed to the factical foundation from which it would emerge. But by grasping this power by means of the notion of existence, Merleau-Ponty does not allow himself in Phenomenology of Perception to understand what he has discovered, for existence is conceived as human existence, that is, as the subject of the movement of transcendence rather than as the very advent of sense. It is finally "man" who "transcends himself toward a new behavior." Existence is grasped as man's facticity, even though the experience to which it refers leads us to overcome the frontal relation of man to being, to overcome the duality of subject and object. Prisoner of a dualist framework, Merleau-Ponty can therefore describe it only in a negative way: it coincides neither with the passivity of the anthropological subject situated in the objective world nor with the pure activity of the constituting subject. But existence is still really that of a subject, or rather is the subject itself, so that the fullness of the experience to which it refers cannot be attained. The notion of pre-personal consciousness, which is a term synonymous with existence, crystallizes the ambiguity. Even though Merleau-Ponty discovers an experience that is no longer personal, an experience in which the category of the person finds itself contested, he grasps it still on the basis of the personal subject, as a negation that is already its affirmation.
(pp. 8-9, Barbaras' emphasis, my bold)
I don't believe Barbaras has adequately established that for Merleau-Ponty human existence, much less existence, equates to the subject, though it is of course attestable. (One should give Merleau-Ponty a chance to explain what he means by "subject," and how he is intending us to understand the concept, for it is not after all transparent.) Additionally, it would be helpful to have an exact citation to Merleau-Ponty's discovery of prepersonal consciousness, because, off the top of my head, that could mean a few things other than what Barbaras' interpretation would have us believe. Prepersonal consciousness could be imminently personal, for instance, pregnant with the who, or with the existence through-sound, or with the sense-giving subject.
If I had to choose between existence and the very advent of sense I would choose existence. However, I'm not sure I have to choose. In what essential way is the very advent of sense not existential? We need to hear more from the anti-existential ontologist before we decide this point. For the moment, let's take a peek at Merleau-Ponty's thoughts on communication (which has perhaps been glossed over), on the existential meaning of words beneath the conceptual meanings of words, a "primordial" silence and the act that breaks the silence, simultaneously an expression and a grasping of a sense. He says:
What I communicate with primarily is not 'representations' or thought, but a speaking subject, with a certain style of being and with the 'world' at which he directs his aim. Just as the sense-giving intention which has set in motion the other person's speech is not an explicit thought, but a certain lack which is asking to be made good, so my taking up this intention is not a process of thinking on my part, but a synchronizing change of my own existence, a transformation of my being.
(Phenomenology, p. 183-184)
"I communicate with . . . a speaking subject." This is not an equation, but neither is it properly prepersonal (though logically one might think a preperson is implied). As I interpret it, nonetheless, it is precisely a with. Even if it is intended to simply state that the speaking subject is the instrument of an ego's communication, the with holds the meaning of a togetherness. Communicationsynkairoticized, perhaps, with the advent of sense, a transfiguration and a trajectoryis existential through and through. What reason have we been given for thinking otherwise? Primordial silence, by which the body is refered to, its taking up of meaning prior to representation? But the body is enigmatic, which is far from saying that the body can never be understood. It secretes in itself a "significance" (p. 197, the quotes are Merleau-Ponty's). Our idea of "sense-giving" should have been transformed by Merleau-Ponty's analysis of the body as expression; the idea of significance has been challenged. The "disclosure of an immanent or incipient significance in the living body extends, as we shall see, to the whole sensible world, and our gaze, prompted by the experience of our own body, will discover in all other 'objects' the miracle of expression" (ibid., Merleau-Ponty's quotes, my bold.) It is Merleau-Ponty who has problematized the object and by implication its other pole, the subject. Barbaras would hardly disagree. Incipience, however, rather than contestation, is the key to Merleau-Ponty's thinking here. To the extent that Merleau-Ponty did abandon existence, there might be other explanations for that besides the concept being superseded by the development of a superior ontology. That said, Barbaras' reading is certainly meritorious and thought-provoking.