It is one of the most complex, interesting and important concepts to understand in the field of modern philosophy and it has been created and developed in his theory, by the German philosopher Immanuel Kant. We refer to the concept of noumenon, which is very abstract and implies a differentiation between thought phenomena and purely sensible ones. For Kant, the noumenon is the object, since it is "in itself", regardless of our way of knowing it, that he calls "the thing in itself". Kant opposes it to the phenomenon, to the object as it is for us, that is, as we know it in terms of the “a priori” forms of sensitivity and understanding.
As is known, Kant gave birth to what is known as German idealism and whose main assumption was the predominance of ideas over the sensible world. Kant argued that thought or noumenon could not be known to the human being and his rational capacity in its entirety, because it was immanent and, therefore, also transcendent.
This means that in itself, the noumenon could be equated with the concept of essence or substance that existed in the philosophy of ancient Greece and that also divided the world of the intelligible with the world of the sensible.
Due to the inability of the human mind to know the real essence of things, Kant argued that the noumenon can only be known, assimilated or apprehended through morality, that is, through a behavior that has the power to signify, or bring benefits for the human condition.
The distinction between phenomena and noumena is fundamental in the Kantian system. In dealing with this question, Kant distinguishes two senses of the concept of noumenon:
- Negatively, "noumenon means something insofar as it cannot be recognized by sensible intuition."
- Positively, it means an "object that can be known through non-sensitive intuition", that is, through intellectual intuition.
Now, as we lack intellectual intuition and we only possess sensible intuition, our knowledge is limited to phenomena and, consequently, the concept of noumenon remains as something negative, as the limit of experience, as the limit of what can be known.. There is no knowledge of things in themselves, of noumena. Access to things is not found in theoretical reason, but in practical reason, as we will see.
The distinction between phenomena and noumena allows us to understand why Kant calls his doctrine " transcendental idealism ": because space, time and categories are conditions of possibility of the phenomena of experience and not real properties or characteristics of the things themselves.
