Kant Lexicon

Noumenon Phänomen (German), nooumenon (Greek)

The distinction of phenomenon and noumenon plays a prominent role in Kant’s writing. The title of his Inaugural Dissertation was On the Form and Principles of the Sensible and the Intelligible World (world of phenomena and world of noumena, respectively.) The concluding chapter of the Transcendental Analytic is entitled “On the Basis of the Distinction of All Objects As Such into Phenomena and Noumena” (beginning at A235/B294). Kant also discusses the distinction in his metaphysics lectures.

In the Inaugural Dissertation, Kant gives the following definitions.

The object of sensibility is the sensible; that which contains nothing but what is to be cognized through the intelligence is intelligible. In the schools of the ancients, the former was called a phenomenon and the latter a noumenon. (§3)

A noumenon is contrasted with a “phenomenon,”, a being of the senses. In the Critique a noumenon is construed either negatively, as not a being of the senses, or positively, as a being of the understanding. A world consisting of phenomena would be a “world of sense,” while a world consisting of noumena (in the positive sense) would be a “world of understanding” (A249). Thus, the division between phenomena and positive noumena is metaphysical.

Negative noumena can be accommodated within Kant’s critical system.

Now the doctrine of sensibility is simultaneously the doctrine of noumena in the negative meaning of the term; i.e., it is the doctrine of things that the understanding must think without this reference to our kind of [sensible] intuition, and hence must think not merely as appearances but as things in themselves. (B307)
The concept of a noumenon is said to be necessary for us “not to extend sensible intuition even over things in themselves, and hence in order to limit the objective validity of sensible cognition” (A254/B310). Thus the negative noumenon serves as a “boundary concept serving to limit the pretension of sensibility” (A255/B310).

A positive noumenon, on the other hand, would have to be the object of an intellectual intuition, which is a faculty that human beings lack. Moreover, we have no way of knowing whether there can even exist a being whose intuition is intellectual.

But that [negative] noumenon is not then a special intelligible object for our understanding. Rather, an understanding to which it would belong is itself a problem, viz., as to how it can cognize its object not discursively through categories, but intuitively in a nonsensible intuition; of such an understanding we cannot frame the slightest presentation as to its possibility. (A256/B312)

It is common for readers of Kant to use the term ‘noumenon” interchangeably with ‘thing in itself’ (Ding an sich). Some might dispute this practice, on the grounds that the notion of a thing in itself is not metaphysical but perhaps “methodological” or “epistemological.”

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