What signified their endless pages about dualism and monism, about phenomenon and noumenon?
But then there is the Ding an sich, the noumenon, or Kantian equivalent for the substance of the soul.
He called it the "noumenon," the "real correlate of matter," and pluralized it as "things in themselves."
But he insisted, as firmly as Herbert Spencer has since done, that the "noumenon" is "unknown and unknowable."
And this meaning is retained in the Kantian philosophy, in which the noumenon is identical with the Ding an sich.
The conception of a noumenon is therefore merely a limitative conception and therefore only of negative use.
The "colligation" of the facts, to use Whewell's phrase, is not a phenomenon, but a noumenon.
The noumenon is a bit difficult to locate; it can be apprehended only be a process of reasoning—which is a phenomenon.
Now, however, Kant proceeds to ascribe this function to the concept of the noumenon.
He will have attained in short to the knowledge of a noumenon, and of the only knowable noumenon.
1796, "object of intellectual intuition" (opposed to a phenomenon), term introduced by Kant, from Greek noumenon "that which is perceived," neuter passive present participle of noein "to apprehend, perceive by the mind" (from noos "mind"). With passive suffix -menos.