. | 1. | the object, itself inaccessible to experience, to which a phenomenon is referred for the basis or cause of its sense content. |
| 2. | a thing in itself, as distinguished from a phenomenon or thing as it appears. |
| 3. | Kantianism. something that can be the object only of a purely intellectual, nonsensuous intuition. |

noumenon
in the philosophy of Immanuel Kant, the thing-in-itself (das Ding an sich) as opposed to what Kant called the phenomenon-the thing as it appears to an observer. Though the noumenal holds the contents of the intelligible world, Kant claimed that man's speculative reason can only know phenomena and can never penetrate to the noumenon. Man, however, is not altogether excluded from the noumenal because practical reason-i.e., the capacity for acting as a moral agent-makes no sense unless a noumenal world is postulated in which freedom, God, and immortality abide.
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