That Philosophy Website

Phenomena and Noumena (Immanuel Kant)

Information: This article explains Immanuel Kant's theory of knowledge, and in particular his distinction between phenomena and noumena.

Immanuel Kant's theory of knowledge has been one of the most influential in modern Western philosophy. His basic premise is that we do not experience the world directly but using certain innate cognitive concepts, which might be said to work like spectacles.

For instance, in order to distinguish between different objects we utilise the concept of space, and in order to make sense of cause and effect we utilise the notion of time. Kant believed it was impossible to experience anything in the world, without employing these two concepts (in fact, we cannot even begin to distinguish ourselves from the world and others without them).

Kant's epistemology has particularly influenced Post-modernist philosophers, who emphasise the relativity of all knowledge, and has even been utilised in the philosophy of religion (see John Hick's pluralist hypothesis).

It is very common to find Kant's theory of knowledge being presumed to be true in the work of modern philosophers.

Kant makes the distinction between things as we perceive them, and things as they truly are in themselves. He called the former phenomena, and the latter noumena.

On the basis that we perceive things through a variety of cognitive filters, Kant argued that we can only attain knowledge of phenomena (this being things as we perceive them). In fact, he even goes so far as to say that without these cognitive filters, the world would be meaningless to us:

'We cannot define [anything] in any real fashion, that is, make the possibility of [an] object understandable, without at once descending to the conditions of sensibility, and so to the form of appearances to which, as their sole objects, they must consequently be limited.' (Critique of Pure Reason: Book II, Chapter III [Brackets mine])

This means that knowledge (or what we can know) is limited by our ability to perceive things. For instance, because we require the cognitive concept of time to distinguish between events going on around us (and to make sense of the things we do), this means we cannot attain knowledge of anything which might be said to be outside of time. In fact, so reliant are we on the concept of time that it is impossible for us to conceive of a timeless realm (such as infinity) without using the concept of time. The best we can do is to say that it is a realm where time has no beginning or end (thus using our standard concept of time in a negative sense).

The use of innate cognitive categories to help us make sense of the world, means that Kant's theory of knowledge is predominantly sense-based. However, this should not be mis-construed to suggest that Kant believed only the sensible (or physical) realm existed. On the contrary, he also believed that behind the realm of appearances (phenomena) there was another realm consisting of things as they truly are, and he called the things in this realm noumena.

Sometimes you find philosophers referring to things in the noumenal realm as the ding an sich, but his is simply the German phrase for 'thing-in-itself' (or things as they truly are).

The word noumena is associated with the Greek word for 'mind' (nous). Kant believed the only way we can begin to understand the idea of a noumenal realm, is through the mind (or intellect).

For instance, although people can experience the same object as having a different shape, colour and texture, depending on where they stand in relation to it, this does not change the fact that (logically) the object must have a true form independent to the way they perceive it. For example, if we turn on a red light over a white sheet of paper we perceive the paper as being red, but this does not change the fact that the paper is still white, even though we cannot experience it this way (due to presence of the red light).

In the same way, Kant argued that there must (logically) be a ding an sich beyond our perception of things. Of course, this thing can never be experienced in the noumenal realm due to the fact that we are only capable of attaining knowledge of things as they appear to us as phenomena. However noumena must logically be there, if for no other reason than to make sense of the world we do (and can) perceive around us.