Though again in the Transcendental Dialect he spoke of pure reason conceiving " ideals " of noumena, he did not mean that a noumenon is nothing but a thought arising only through thinking, or projected by reason, but meant that pure reason can only conceive the " ideal " while, over and above the " ideal " of pure reason, a noumenon is a real thing, a thing in itself, which is not indeed known, but whose existence is postulated by practical reason in the three instances of God, freedom, and immortality.
But it is not maintained, on the side either of phenomena or of noumena; and hence its tendency to materialism.
Or is it simply a reiteration of his sceptical contrast between phenomena and noumena, and of his confinement of (valid) knowledge to the former?
But they disagreed with Kant, and agreed with Fichte about things in themselves or noumena, and contended that the mental things we know are not mere phenomena of sense, but noumena, precisely because noumena are as mental as phenomena, and therefore can be known from similar data: this was the central point of their noumenal idealism.
Starting from Fichte's " Wissenschaftslehre," Schelling accepted the whole process of mental construction, and the deduction that noumena are knowable products of universal reason, the Absolute Ego.
Its essence, as stated by Kant, was to reduce the logical use of reason to mental phenomena of experience in speculation, in order to extend the practical use of reason to the real noumena, or things in themselves, required for morality.
I have champed up all that chaff about the ego and the non-ego, noumena and phenomena, and all the rest of it, too often not to know that in attempting even to think of these questions, the human intellect flounders at once out of its depth."
The doctrine of space and time as forms of sense-perception, the reference of both space and time and the pure intellectual notions to the laws of the activity of mind itself, the distinction between sense and understanding as one of kind, not of degree, with the correlative distinction between phenomena and noumena, - all of these reappear, though changed and modified, in the Kritik.
The relation between phenomena and noumena in the Kantian system does not in the least resemble that which plays so important a part in modern psychology - between the subjective results of sense affection and the character of the objective conditions of such affection.
This idea of an intuitive understanding is the definite expression for the complete explanation which reason demands, and it involves the conception of a realm of objects for such an understanding, a realm of objects which, in opposition to the phenomena of our relative and limited experience, may be called noumena or things-in-themselves.
Assuredly, the difficult section of the Kritik, on the ground of the distinction between phenomena and noumena, would not have led to so much misconception as it has done, had Kant then brought forward what lies at the root of the distinction, his doctrine of reason and its functions.
The distinction between phenomena and noumena is, therefore, nothing but the expression of the distinction between understanding and reason, a distinction which, according to Kant, is merely subjective.
C. As to existence, Kant's position is the wholly illogical one that, though all known things are phenomena, there are things in themselves, or noumena; things which are said to cause sensations of outer sense and to receive sensations of inner sense, though they are beyond the category of causality which is defined as one of the notions uniting phenomena; and things which are assumed to exist and have these causal attributes, though declared unknowable by any logical use of reason, because logical reason is limited by the mental matter and form of experience to phenomena; and all this according to Kant himself.