Unum quid (Descartes)

Latin: "one and the same thing"; "a certain something one." Descartes's name in the Sixth Meditation (AT VII 81 — the French version has "une même chose" / "un seul tout," AT IXa 12, 64) for the substantial union of the soul and the body — a third notion irreducible to either res cogitans or res extensa, with its own way of being conceived. The concept becomes the shared anchor of Part I of morin-2022-mp-nancy-sense-being: MP reads it (Ch 1) as the lived body's mode of being that requires its own (non-dualist) framework; Nancy reads it (Ch 2, Ego Sum 1979) as the utterer of "ego sum" — neither res cogitans nor res extensa, but a something that is neither-soul-nor-body (ES 107).

Key Points

  • A third notion (Sixth Meditation): the union of soul and body is not a composite of two substances but a third irreducible mode requiring its own conceptual register. Descartes signals this in the "Letter to Elisabeth" of 28 June 1643 (cited by MP and Nancy) — "the union" is grasped neither by the senses alone (which give only the body) nor by understanding alone (which gives only the soul) but by life itself / "natural inclination."
  • MP's reading (Ch 1 §1 of Morin): the unum quid is the substantive name for "the lived body" — what is reached through MP's circular reading of the Meditations, where the Sixth (union) grounds the First (doubt), not the other way round. The meditator must already be a body to begin meditating. The unum quid is the irreducibility that MP's phenomenology of perception excavates.
  • Nancy's reading (Ch 2 §1 of Morin): the unum quid is what utters ego sum; not the res cogitans, not the thinking substance. The ego is teleiopoetic (Derrida-style — produced by the utterance, not preceding it). The unum quid is "something that is neither-soul-nor-body" (ES 107), an opening (figured as the mouth) that articulates ego. See *rien* (Nancy) for the parallel etymological move.
  • The French addition (AT IXa 62): "this I, that is, my soul, by which I am what I am, is entirely and truly distinct from my body." Nancy reads this as authorising two distinctions: (a) between me and my body; (b) between what I am and that by which I am what I am (ES 95–6).
  • Tied to the operative cogito (MP NC 251): MP's late 1960–61 Cartesian-ontology lecture course returns to the unum quid via the operative / vertical / "thick" cogito — a "third domain of being" between immediate being and negation. The unum quid is no longer just the lived body but the mode of being of the operative cogito.

Details

The shared anchor

Per Morin Intro §3 and Part I, the unum quid is the one place where MP and Nancy explicitly converge — both read it as the third notion the metaphysical tradition cannot accommodate. They diverge on what to do with it:

  • MP: the unum quid is the lived body; its philosophical articulation requires a new (non-dualist) framework — the Phenomenology of Perception, the late ontology of the flesh.
  • Nancy: the unum quid is the opening (the mouth as figure) by which existence is à-soi; the framework is the partes extra partes radicalised and the corpus corporum.

Both refuse the Cartesian "ontology of the object" + the modern reconstruction of the subject; both retain the unum quid as the conceptual anchor. The divergence comes in how they extend the third-notion-status — for MP toward presumptive unity, for Nancy toward irreducible dislocation.

Why the circular reading matters

MP and Nancy share the circular reading of the Meditations: rather than reading from the First (doubt) → Second (cogito) → Sixth (union), they read from the Sixth back. The meditator must already be a body — already in the union — to begin meditating. MP cites this as the move that lets him recover the unum quid as the ground of the cogito, not its consequence. Nancy frames it differently — the ego of the Second Meditation can be uttered only by the unum quid of the Sixth.

The convergence is structural: both refuse the analytic dissection of the union (which "renders unintelligible" — VI 268) and read the union as the first term that gives intelligibility to the rest.

The Heideggerian objection blocked

Per Morin Ch 2 §1, Heidegger reads the cogito as the inaugural moment of modern metaphysics — the "I" as sub-jectum, the underlying subject of representation; certainty becomes the measure of truth ("Metaphysics as History of Being," in End of Philosophy 28–30). Nancy's reading disrupts this Heideggerian objection: the ego is NOT the thinking substance but the unum quid, the "gaping mouth that unfounds the subject in the very moment of its foundation." So the modern subject Heidegger criticises was never what Descartes inaugurated — it was a later reconstruction that flattened the unum quid.

Connections

  • anchored in rene-descartes Sixth Meditation (AT VII 81; AT IXa 12, 62) — and the "Letter to Elisabeth" 28 June 1643.
  • read by maurice-merleau-ponty as the lived body's third-notion-status (Ch 1 of Morin); ground of the circular Meditations reading.
  • read by jean-luc-nancy as the utterer of ego sum (Ego Sum 95–6, 107, 109–10); not res cogitans but the opening (mouth).
  • anticipates MP's tacit-cogito (and its self-criticism in VI 171, MP's "tacit Cogito is impossible") and the operative cogito of NC 251.
  • blocks Heidegger's reading of cogito as sub-jectum (Nancy ES 99; End of Philosophy 28–30).
  • connects to empietement — the unum quid is the original anti-Cartesian moment whose extension is MP's late ontology of encroachment.
  • connects to Nancy's corpus-corporum — the unum quid radicalised becomes the body as collection-of-zones.
  • connects to Nancy's à-soi / being-to-itself / différance — the unum quid read as the originary opening to exteriority.

Open Questions

  • Does MP retain the unum quid terminology in the late ontology, or does he replace it with flesh / Ineinander? The 1960–61 NC lectures return to it explicitly (NC 251, 257); the late VI uses "flesh" more often. The genealogy is worth tracking.
  • Is Nancy's reading of the unum quid compatible with the standard "Letter to Elisabeth" reading? Most commentators read the union as a practical notion (lived rather than understood); Nancy reads it as a third ontological notion. The hermeneutic stakes are high.
  • What does the unum quid mean for cognitive science / philosophy of mind? Both MP and Nancy refuse mind-body dualism but in incompatible ways; the unum quid might be a productive anchor for contemporary 4E cognition / extended-mind research.

Sources

  • morin-2022-mp-nancy-sense-being — Ch 1 (MP's circular reading); Ch 2 (Nancy's Ego Sum reading); Intro §3 (the convergence). Primary anchors: ES 95–6, 99, 107, 109–10, 112; AT VII 15, 25, 78, 81; AT IXa 12, 62, 64; NC 251, 257.