Noumenon

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The noumenon is the object considered as it is in itself, apart from the way it appears to a perceiving mind. The word entered modern philosophy through Immanuel Kant, who used it as the formal counterpart to the phenomenon — the thing as it is given in experience — and who often spoke instead of the Ding an sich, the thing-in-itself. Behind every appearance, Kant held, lies something that appears; what that something is, in its own nature, the human intellect is not equipped to know.

The term is older than Kant and his use of it bent it sharply. In Greek, nooumenon meant simply that which is grasped by nous, the intellect, as opposed to what is taken in by the senses — a Platonic vocabulary in which the intelligible was the more real, the world of changeless forms behind the flux of sensation. Kant kept the contrast between thought and sense but reversed the optimism. For Plato the intellect could reach the higher order; for Kant the mind’s reach was precisely the problem. Space, time, and the categories through which experience is organised, he argued, belong to the knowing subject, not to the world apart from it. They make experience possible and, in the same stroke, confine knowledge to appearances.

So the noumenon arrives mainly as a limit. Kant distinguished a negative sense — the thing-in-itself simply as the bound beyond which knowledge cannot pass — from a positive sense, an object of some non-sensory intellectual intuition, which he denied that human beings possess. The concept marks where cognition stops. It cannot be filled in. This is the source of a difficulty his readers have worried at ever since: if the thing-in-itself is unknowable, how can it be said to exist, or to cause appearances at all, since causation is one of the very categories Kant restricts to the phenomenal world? The objection was pressed early, by Jacobi and others, and the German Idealists who followed — Fichte, Hegel — took the unknowable noumenon to be the unstable point on which the whole system turned, and built their philosophies by trying to dissolve it.

Later thought kept the word and shifted its weight. Schopenhauer accepted the distinction but claimed, against Kant, that the thing-in-itself could be known from within, as will. Scholarship continues to divide over what Kant meant: whether phenomena and noumena are two distinct sets of objects, or one set of objects considered in two ways — the “two-world” and “two-aspect” readings — a dispute that turns on close reading of difficult passages and remains open.

The idea reaches well beyond academic philosophy. Wherever a tradition holds that the real lies behind or beneath what the senses report — the veil of appearance in Indian thought, the hidden God of the mystics, the conviction running through several currents that ordinary perception is a kind of sleep — the structure rhymes with Kant’s. The resemblance is worth marking and easy to overstate. Kant was drawing a boundary around knowledge, not promising a way across it; the mystic claims to cross. What they share is only the conviction that the world as given is not the world entire.

→ Related: Nous · Immanence · Hypostasis · Gnosis