Nancy draws a distinction between the body and the existence of the body, which at first blush may appear to set his thinking apart from other approaches to embodiment. He equates the reality of freedom with the existence of the body, and says:
The existence of a body is a free force which does not disappear even when the body is destroyed and which does not disappear as such except when the relation of this existence to another and destructive existence is itself destroyed as a relation of existences, becoming a relation of essences in a causality: such is the difference of relation between the murderer and his victim, and the difference of nonrelation between the exterminator and his mass grave. This force is neither of the "spirit" nor of the "body"; it is existence itself, impossible to confuse with a subjectivity (since it can be deprived of consciousness and will) or with an objectivity (since it can be deprived of power).
There's room here to explore the ethics of abandodment and also withdrawal, to question whether Nancy's communitarianism is up to the task of outlining a livable ethics. I'd like to stay focused, however, on his notion of the body and the kind of materialism he calls ontological. He argues that because existence as such has its being in the act of existing, i.e. as a praxis, it has the actual character of a force. Thinking the force of existence implies "the thought of a transcendental materiality, or if we prefer, an ontological materiality: the withdrawal of being as a material Setzung of singularity, and the difference of singularities as a difference of forces. Prior to every determination of matter, this materiality of existence, which sets down the fact of freedom, is no less endowed with the material properties of exteriority and resistance" (p. 103). So there is something about Nancy's existence of the body, in contrast to the body as such, which is impervious or resistant to outside forces even the annihilation of the body can't touch the existence of the body.
I think a careful reading of the phenomenologists of embodiment (Merleau-Ponty, Henry, Patočka) would show that their conceptions of the body are praxiological in key respects, are neither subjective nor objective, and tend to be existential. But where they would recognize a distinction between the body as object and the body as it is lived, Nancy has a distinction between the existence of the body and the body. Is Nancy's formulation simple and elegant, or is it a kind of metaphysical trickery? If we want to appreciate its elegance we need to be mindful of all that Nancy has said about existence. That's a dizzying prospect. Here's a start: once existence neither precedes nor follows essence, but precisely "lies in," that is constitutes essence, then, "Freedom can no longer be either 'essential' or 'existential,' but is implicated in the chiasmus of these concepts: we have to consider what makes existence, which is in its essence abandonded to a freedom, free for this abandonment, offered to it and available in it" (p. 9). Nancy's topic is freedom, and to mind the chiasmus of existence and essence we can't ignore this; however, the idea of the persistence of the existence of the body as a free force strikes me as similar to a concept of the soul, an existential soul, but precisely a soul. And though I am unsure of exactly what Nancy thinks about the soul, I wonder whether his ontological materialism is a materialism solely of living organisms who maintain a transcendental relationship to "dead" matter, or, indeed, whether it is a materialism only of those who are born. Nancy says, cryptically, that "all existence is new, in its birth and in its death to the world" (p. 11). What does death matter to an existence that is always and forever new?
Does an ontological materialism for which "dead" matter ceases to matter warrant being called a materialism? It is a kind of dynamism, which may be implied in materialism but doesn't itself necessarily imply materialism. It is significant, I think, that Nancy chooses to come down on the side of materialism, and that he sees exteriority and resistance as material properties. I ask myself whether Maine de Biran was a materialist, and the question seems unduly limiting. For all I can tell, Nancy's ontological materialism could also be a materialism of the soul. I remind you, dear reader, that I am agnostic about animism and other doctrines of the soul, and ignorant of theology, though of course I have some curiousities. So, sticking with Nancy's terms, I am being asked to believe in freedom and to believe in its chiasmatic relation to existence and essence, concepts which might also require some belief. The question for me though is not quite one of belief, but of what kind of commitment I should have to freedom even though I don't fully understand it. What kind of commitment does an ontological materialism call for?