Saturday, 2 July 2011

Kant’s noumenal realm reconsidered in the light of contemporary developments in physics

Philosophers have been uneasy about Kant’s notion of a noumenal realm existing alongside the phenomenal realm as part of our cosmos since the time when he first proposed it.  For them, it seemed that there is nothing to justify its existence.  In this essay, I, however, propose that Kant might have been right after all.  It seems quite possible that Kant’s noumenal realm could be identified with the higher dimensional structure of the universe that has been postulated in contemporary theoretical physics.  I look into the implications of such an identification.


Immanuel Kant (1724-1804) is one of the great names in modern philosophy and he had an enormous influence on all later philosophers.  Even post-modern philosophy is to a large extent a reaction against the Kantian perspective, with regards to both his grounding of science as well as morality in the transcendental human subject.  Central to Kant’s philosophy is the concept of a “noumenal” realm in which the freedom to both think and act are situated.  Although we could not gain any true knowledge about this realm, not even about the existence thereof, he did postulate it to account for the human ability to both creatively imagine and freely act in accordance with the moral law (and thus be responsible for one’s actions). 

The possible existence of a noumenal realm in a realist sense was, however, increasingly viewed as an unlikely possibility.  Shortly after Kant philosophers started rejecting this in their philosophy.  But was Kant wrong?  In this essay, I propose that Kant might be right after all!  In contemporary physics, it has been theorized that, even though our perception of the world is restricted to the four normal space-time dimensions, there could be other higher dimensions interwoven in the cosmos to which we have no access.  This higher dimensional structure of the cosmos corresponds to a remarkable degree with the noumenal realm that Kant postulated.  If we allow for this identification the implications for philosophy are profound.

In this essay I first give a broad overview of Kant’s view, focusing on his perspective regarding the phenomenal and noumenal realms.  I discuss the implications of both the non-existence as well as the existence of the noumenal realm.  I show why the noumenal realm could be identified with the higher dimensional structure of the universe.  I also make some proposals as to how Kant’s views, which were formulated in a Newtonian framework, could be logically adapted to incorporate contemporary developments in theoretical physics.  When this is done, Kant’s philosophy could provide a powerful framework within which the contemporary developments in physics could be interpreted.  Finally, some implications of this approach are discussed.            
Phenomena and noumena

According to Kant our world in its totality could be divided into two parts, namely the world that we empirically observe, consisting of all sorts of things, called phenomena or appearances, and an underlying part which is inaccessible to our senses and in which the “things in themselves” (as they in essence really are), called noumena, are situated.  The things in themselves (noumena) form the basis in which things (phenomena) are grounded.  Kant wrote in the Critique of Practical Reason: “Letting objects of experience as such, including even our own subject, hold only as appearances but at the same time… putting things in themselves at their basis” (Kant 1997:5).  Kant also refers to these as the supersensible and sensible, or the archetypal and ectypal worlds: “The former [supersensible] could be called the archetypal world (natura archetypa) which we cognize only in reason, whereas the latter [sensible] could be called the ectypal world (natura ectypa) because it contains the possible effect of the idea of the former” (Kant 1997:39).  

As with all objects, humans are situated in both worlds.  Thus they could view themselves under two different, even contradictory, aspects, namely as phenomena subject to the laws of nature (especially of causality), situated in normal time and space, but also as noumena which could be thought of as subject to other laws (especially of freedom), situated outside normal time and space (Tarnas 1991:352).  Andrews Reath says: ”The distinction between appearances and things in themselves, along with the claim that spatio-temporal properties and laws do not represent objects as they are in themselves, creates room for the thought of noumenal objects subject to laws that are different in kind from those governing spatio-temporal events” (Kant 1997:xi).

Humans are capable of comprehending the world because they have a priori interpretive principles or forms of thought called “categories of the understanding” (for example of cause and effect, substance, quantity, relation) which unite the manifold given in intuition in consciousness (Kant 1934:186; Tarnas 1991:344).  Kant allowed two types of intuitions, namely intellectual and sensible intuitions, which are directed towards the noumenal and phenomenal worlds respectively (Kant 1934:187).  Noumena are objects of intellectual intuitions (Kant 1934:187l; i.e. a direct intellectual access not possible for humans). They are not necessarily grounding appearances (one could think of God or angels) (Ward 2006:102).  Since they are unschematized (i.e. they could not be placed in normal space and time), they are not determinate objects. 

The only intuitions that could lead to real knowledge are the sensible ones.  The mind is only able to place such intuitions of phenomenal objects (“things”) within the normal space-time framework, allowing them from a human perspective to obtain “objective” existence (Kant 1934:190; Caygill 1995:394).  This means that pure reason is restricted in its ability to provide valid knowledge; it could only provide knowledge of the empirical world of phenomena. In this way, Kant established the boundaries of the application of pure reason.  Science could never attain knowledge of all of reality – the things as they are in themselves are outside its reach.  This, however, does not mean that we cannot think things in themselves.  We can.  But, as Kant said in the Critique of Pure Reason: “[They] must ever remain unknown to us” (Kant 1934:190).  We can at most “belief” that such things exist.

Although humans are restricted in their use of pure reason, Kant proposed another form of reason, namely “practical reason”, for “practical use”, that could be used to ascribe certain properties to the noumenal realm (Kant 1997:5).  Practical reason could be used to account for those practical realities of our lives that could not be established through pure reason, for example, that humans have the freedom to act rationally.  Kant was of the opinion that such freedom is a practical reality of human lives, forming the basis of our rationality: “The concept of freedom, insofar as its reality is proved by apodictic law of practical reason, constitutes the keystone of the whole structure of a system of pure reason” (Kant 1997:3).  Both the spontaneous activity of our imagination that synthesizes concepts and intuitions, as well as our will, exhibits such freedom.  Although such a concept of freedom falls outside the scope of any knowledge claims (as established through pure reason), the assertion thereof is nevertheless still rationally based.
Although the natural law of causality rules out the possibility of freedom in the phenomenal world, there is no reason why it could not be ascribed to the noumenal dimension.  In fact, it is exactly the possible existence of such a dimension that allows us to account for human freedom.  Reath writes in this regard: “Human actions, when considered as noumena, could be regarded as resulting from transcendental freedom … The grounds for ascribing freedom to ourselves come from our recognition of the authority of moral norms, and this ascription is made for practical purposes, as part of our self-conception as rational agents” (Kant 1997:xii/xiii).  This implies that the laws governing the noumenal world could to some extent be indirectly established through practical reason. 

The existence/non-existence of the noumenal realm

There are two possible ways to take the Kantian notion of a noumenal realm existing within the framework of our world in its totality.  One could reject such a possibility.  Until a few decades ago philosophers had no reason to accept such a possibility since there was no empirical reason to postulate it except maybe a moral one (the one Kant used).  In this case one could view Kant as following in the footsteps of Plato who postulated the existence of two worlds, namely one of being (of forms) and one of becoming, which in his later works, especially the Timaeus (Ostenfeld 1982:75), are not too dissimilar to Kant’s worlds of things in themselves (noumena) and things (phenomena).  Together with Plato’s ideas, Kant’s ideas in this regard could then be disregarded as “metaphysics”.     

Even if one rejects the notion of a noumenal realm, one could work with the notion of “transcendental” as referring to that which all people share (i.e. transcendental categories of understanding).  This is the path that many philosophers have followed, especially in analytic and phenomenal philosophy.  In this case, one still has to accept that the structures of the human mind are not fixed and timeless as Kant is supposed to have taken them, but are historically determined.  Many factors influence the non-absolute categories namely habit, history, culture, social class, biology, language, imagination, emotions as well as the unconscious (Tarnas 1991:184). 

In positing a noumenal realm in which the human self is also embedded, Kant connected the subject in a very profound way with the universe in which s/he is situated.  Some philosophers explored this possibility further even though they rejected the possibility of the existence of the noumenal realm: Fichte, Schelling and Hegel suggested that the cognitive categories of the mind were in some sense the ontological categories of the universe (Tarnas 1991:353).  In a way, they still held that the categories are embedded in the cosmic (although not noumenal) structure of the universe.  But as soon as this idea lost influence, the human subject became adrift and no direct contact between the human mind and the intrinsic structure of the universe could be assumed (Tarnas 1991:350).  In this way, the subject became decentered from its position as a basis for knowledge.  The acknowledgement of the impact of the unconscious on all our conscious actions opened the door for the post-modern philosophical perspective.

The noumenal realm as an archetypal world

But what are the implications of an acceptance of the existence of such a noumenal realm?  In this case, one could build on the Kantian foundation.  Instead of reducing the Kantian insights to their bare essentials, one could also explore the possibilities that Kant left untouched, using, for example, new developments in psychoanalysis.  In accordance with Kant’s notion of an archetypal world (natura archetypa) in which the categories of the mind are situated, C. G. Jung developed a very similar idea involving the unconscious.  Paul Kugler writes: “Kant’s categories (time, space, number, and so on) provided the a priori structures necessary for reason itself.  Jung extended the subtle implications of Kant’s Critique of Pure Reason to the realm of depth psychology, positing archetypes as the a priori categories of the human psyche” (Kugler 2008:86).  He quotes from Jung’s own writings to affirm this:

“One could also describe these forms as categories analogous to the logical categories which are always and everywhere present as the basic postulates of reason.  Only, in the case of our `forms’, we are not dealing with categories of reason but categories of the imagination…  The archetypes are, so to speak, organs of the prerational psyche.  They are eternally inherited forms and ideas which have no specific content.  Their specific content only appears in the course of the individual’s life, when personal experience is taken up in precisely those forms” (Jung 1953-77:517-518).

Richard Tarnas writes in a similar vein: “[A] new focus on the inner workings of the psyche reflected as well an increasingly sophisticated concern with those unconscious structures within the mind of the subject that were determining the ostensible nature of the object – a continuation of the Kantian project on a more comprehensive level… In the course of analyzing a vast range of psychological and cultural phenomena, Jung found evidence of a collective unconscious common to all human beings and structured according to powerful archetypal principles… [J]ung’s granting the status of empirical phenomena to psychological reality was itself a major step past Kant, for he thereby gave substance to ‘internal’ experience as Kant had to ‘external’ experience: all human experience, not just sense impressions, had to be included for a genuinely comprehensive empiricism” (Tarnas 191:383-5).                   

Kant focused only on the conscious mind and then allowed, among all possible non-sensual intuitions, only for intellectual intuitions of noumenal objects.  He did not allow for other non-sensual intuitions that could, for example, be associated with the unconscious part of the mind and which could also be directed towards the noumenal (archetypal) realm.  Furthermore, although Kant refers to the phenomenal/empirical self as distinct from the transcendental self that is associated with the universal structures of the mind, he did maybe not position the personal conscious clearly enough within this collective framework.  Jung did this for the personal and collective unconscious: “[The] personal unconscious rests upon a deeper layer, which does not derive from personal experience and is not a personal acquisition but is inborn.  This deeper layer I call the collective unconscious.  I have chosen this term ‘collective’ because this part of the unconscious is not individual but universal” (Jung 1990:299). 

The “collective” Kantian structures of the mind could be seen in the same way.  They are timeless, not in the sense that they stay the same over time throughout history (as some have wrongly interpreted them), but in the sense that they lay outside the normal time-space framework in the noumenal dimension.  They are also dynamic – allowing for example, for schematization in a contracted or bent space-time framework (in accordance with Einstein’s theories of relativity).  Furthermore, although they themselves do not incorporate a personal component, they underlay the personal component that is situated in both the noumenal and phenomenal realms, and which integrates these. The unconscious part of the mind only influences this personal component of the conscious.  The reason why a community of scientists could reach rational agreement is that they, in spite of the personal component, all share the underlying impersonal, universal, collective structures of understanding.  When the categories of understanding are understood in this way, the validity of human knowledge could maybe be secured.  

The problem with the Jungian concepts is that they have empirical validity only in the psychological sense.  Tarnas writes in this regard: “Depth psychology had perhaps rendered a deeper inner world for modern man, but the objective universe as known by natural science was necessarily opaque, without transcendent dimensions” (Tarnas 1991:367).  But what if the archetypal realm that corresponds with Kant’s noumenal realm does indeed exist?  This could imply that the human mind does in effect have access to this realm, although not in the same way that it has to the phenomenal world.  Kant allowed for this on the intellectual level (albeit not for humans); Jung extended it to the unconscious level.  Kant only allowed for a negative characterization of the noumenal realm, i.e. in a relative way as “that which is the cause or ground of appearances” (Ward 2006:100; Kant 1934:188), but it seems that Jung allows us to also characterize it in a positive way. 

Archetypes are schematized in the form of archetypal images existing in normal space and time.  This could imply that one could get true knowledge (in the form of archetypal images) from the noumenal realm.  Furthermore, if the subject’s mind is embedded in the noumenal realm of the cosmos, s/he is not removed from the world in which s/he is situated.  It is from its groundedness in the noumenal realm that the self accesses the world.

But what reason does one have to postulate the existence of such a noumenal realm?  I propose that this realm should be viewed as nothing but the higher dimensional structure of the cosmos as it is presently theorized in quantum physics.  And it seems to me that we have good reasons to accept this identification.

Relating the noumenal realm to the higher dimensions of theoretical physics

The Polish mathematician Theodor Kaluza was the first to propose (in 1919) that the structure of the universe contains higher dimensions.  (Interesting enough, as with Kant, he was from the University of Köningsberg).  He posited that space dimensions could come in two varieties, namely as large, extended and therefore directly manifested (the normal variety), as well as small and curled up (higher dimensions).  The Swedish mathematician Oskar Klein later refined his work.  They suggested that embedded in the fabric of the universe, at every point thereof, these extra dimensions exist alongside the others (Greene 2000:185-190).

Since the mid-1970’s higher dimensions have become a central part of theoretical studies in physics.  A larger number as well as different shapes have been proposed for such space dimensions.  Even other time dimensions could not be excluded.  In string theory elementary particles are envisioned as tiny strings that vibrate in both large, extended space dimensions as well as in the tiny, curled-up ones.  In fact, the structure of these higher dimensions, its extra-dimensional geometry, determines the fundamental physical attributes like particle masses and charges that is observed in the normal large space dimensions of common experience (Greene 2000:206).  The theoretical physicist Brian Greene writes: “The geometrical form of the extra dimensions plays a critical role in determining resonant patterns of vibration – which appear to us as the masses and charges of elementary particles” (Greene 2000:206 – my accentuation).                          

Now this corresponds remarkably with Kant’s postulate that the noumenal aspect of the cosmos, not only forms the basis and cause of the phenomenal world of observation, but that the phenomena flows from the noumena (Ward 2006:100).  In both cases there is a reference to an inaccessible dimension of our world that forms part of the fabric of the cosmos and which determines what our world of “appearance” looks like (a word Brian Greene also uses!).  Andrew Ward sums up the Kantian view: “[B]y taking the noumenal ground as ultimately responsible for the design of the whole spatio-temporal world, including its physical laws, we can give a purposive explanation for the extraordinary large number of diverse natural forms” (Ward 2006:218).  This is in effect what Greene says.

This brings us to Kant’s proposal that deterministic behaviour is to be associated with the world of phenomena and freedom with the world of noumena.  Is there any reason to accept that freedom (in contrast with determinism) should be associated with the higher dimensions in physics?  Here I would like to refer to the Schrödinger equation, according to which particles like electrons and photons are spread out “in a strange multi-dimensional ‘hyperspace’” (Pine 2006:222).  Some physicists like David Bohm takes this serious as referring to what actually happens (although he views the dimensions differently from string theorists).  When the wave-function “collapses”, the unobserved particle-wave which is somehow located multidimensionally, instantaneously collapse to a single unpredictable point in three-dimensional space.  

What is of interest to us, is that the location/position where the particle will become manifest could not in any way be determined beforehand – it happens in a random manner.  It is only possible to calculate the probability of a particle-wave collapsing at a certain location.  If the particle is in fact situated in part in higher dimensional space as has been proposed, then one could say that the random manifestation thereof in three-dimensional space results from the “freedom” inherent in that dimensions.  This corresponds to some extent with what Kant has said, namely that the free play of our imagination and our free will, as observed in our actions in the phenomenal sphere, originates in the noumenal dimension where the law of freedom reigns. 

As for the imagination, there is some evidence that its ability to produce concrete archetypal images from the dynamic underlying archetypal structures, takes place in a way not too different from what is observed in quantum physics, namely in a random (free) manner, restricted to certain particular outcomes.  Jung, following Kant’s lead (who in his Critique of Judgment made much of the free play of the productive imagination), used a technique that he called “active imagination” to stimulate the mind’s archetypal capabilities.  He writes:

“[I] took up a dream image or an association of the patient’s, and, with this as a point of departure, set him the task of elaborating or developing his theme by giving free reign to his fantasy.  This, according to individual taste and talent, could be done in any number of ways, dramatic, dialectic, visual, acoustic, or in the form of dancing, painting, drawing or modeling.  The result of this technique was a vast number of complicated designs… I was witnessing the spontaneous manifestation of an unconscious process… The chaotic assortment of images that at first confronted me reduced itself in the course of the work to certain well-defined themes and formal elements, which repeated themselves in identical or analogous form with the most varied individuals” (Jung 1990:74/5). 

As for the free will, there is obviously a great difference between the “free” (random) manifestation of particles and a “free” will.  One could, however, propose a very complex interplay of noumena and phenomena, combining freedom and determinism, in the framework of the human mind/brain resulting in humans having a free will.  If this is the case, the freedom manifested in the will is just a much more complex expression of the same basic freedom that is manifest in quantum physics.

The implications for epistemology and ontology

What are the implications for physics, both with regards to epistemology and ontology, if Kant’s noumenal realm corresponds to the higher dimensional structure of the cosmos?  To what extent would one then be able to accommodate developments in quantum physics within the framework of Kantian philosophy?  And what further adaptations to the Kantian perspective could be proposed to bring it in line with quantum physics?  To answer these questions we could first refer to the two well-known interpretations of quantum physics.

The interpretation of the wave-particle duality and how it manifests itself in quantum physics has divided the physics community.  Some physicists, like Niels Bohr and Werner Heisenberg, have formulated the so-called Copenhagen interpretation, according to which observations on the subatomic level present us with a new epistemological discovery, namely that we have reached a barrier in our attempt to describe nature in terms of human concepts derived from ordinary experience (Pine 2006:226).  According to them the descriptions that we normally use to describe nature, like “particle”, “wave”, “position”, “mass” and “spin” involve assumptions about space and time that is not valid on that level.  At most, we could arrive at complementary views of reality. 

This view builds on the philosophical tradition derived from David Hume, according to which the question of what is real is unanswerable (Pine 2006:229).  We could describe the empirical world of observation, but we do not have access to the world as it really is.  Therefore, one should accept that between measurements, when the particle-wave propagates, there is nothing that could be known, i.e. that could be conceptualized in human terms.  Only when the particle is observed, when we could measure it, does it become an object in the true sense of the word.

One could propose that the limit that has been reached is not so much due to the smallness of the particles.  If it was only the smallness of the particles that was the issue, one could always have the expectation that new technology would enable us to overcome such a barrier in extending our observational reach.  But the Copenhagen interpretation clearly refers to a more fundamental barrier.  One could propose that the barrier that has been reached is the higher dimensional structure of the cosmos in which the subatomic particles is (at the very least) partially situated.  This could imply that physicists have experimentally become confronted with things situated in these higher dimensions, that is, with things as they truly are.

If we allow that this higher dimensional structure of the cosmos is the same as the noumenal realm that Kant postulated, then his philosophy is applicable to situations like these.  He said exactly what the Copenhagen interpretation acknowledges, namely that we have no direct experimental access to things situated in this dimension.  Also, in accordance with the “complementary views of reality”, he held that different sets of rules apply in the phenomenal and noumenal realms.                
Not all physicists agreed with the Copenhagen interpretation.  Albert Einstein, for example, disagreed.  Einstein rejected the view that a true barrier to knowledge had been reached.  He believed that “There is nothing so far removed from us to be beyond our reach or so hidden that we cannot discover it” (Pine 2006:225).  The human mind would always be able to conceptualize at least the most likely hypothesis about the nature of reality.  Using mathematical models and experimentation, physicists have proposed that we could arrive at a better and better understanding of the hidden forces acting on the subatomic level.  It is exactly in this domain of theoretical physics where the existence of a higher dimensional structure of the cosmos has been proposed.        

This view could also, to some extent, be accommodated in the Kantian perspective if the higher dimensional structure of the cosmos is equated with his noumenal realm.  Kant allowed that we could rationally think and conceptualize this realm.  But according to Kant we cannot arrive at any knowledge of this realm based on pure reason.  Kant, however, did allow us to say something about this realm using “practical reason”. The laws governing the noumenal world could to some extent be indirectly established through practical reason. 

Although Kant only applied practical reason to human freedom (morality), one could propose that it could also be applied to science.  This implies that one could, in spite of what Kant proposed, maybe also positively characterize the noumenal realm in physics (when we equate it with the higher dimensional structure of the universe).  Kant did not foresee that one day we would be able to indirectly access the noumenal realm to the extent that we are presently doing.  And it seems that it is through practical reason (not in the moral sense) that the identification between Kant’s noumenal realm and the higher dimensional structure of the cosmos as it is described in theoretical physics can be established.


It has been more than 200 years since Kant developed his philosophy.  The world has changed a lot.  We have moved beyond the Newtonian view of the world.  Einstein’s theories of relativity and quantum physics have changed our view of the world.  It has been a long time since philosophers have dropped Kant’s notion of a noumenal world existing alongside the phenomenal world.  Could it be true that Kant was right after all?  That his philosophy is not only compatible with our contemporary view of the world, but that the noumenal realm that he postulated is nothing but the higher dimensional structure of our universe that have recently been taken seriously by theoretical scientists? 

In this essay I proposed that this is indeed the case.  After giving a broad overview of the Kantian view, I made some proposals how his philosophy could be adapted (one should rather say extended) to incorporate new developments in psychoanalysis as well as physics. The existence of the noumenal realm opens up the possibility that our knowledge could indeed to some extent be grounded in the human subject, not as standing apart from the world, but as being part of the world.  His philosophy also, not only provides a unified perspective on our world that could incorporate disciplines as far apart as psychoanalysis and physics; it also enables us to reconcile the different interpretations of quantum physics.

If my proposals are accepted, the implications thereof are profound.  It implies that philosophy has taken a wrong turn when it rejected the noumenal realm.  Since this provides the natural ground for knowledge, at least some of what has been done since then leading to the scepticism of post-modernism should be reconsidered.  The adapted Kantian perspective could provide a powerful framework within which the contemporary developments in physics could be interpreted. Lastly, the existence of such a realm reinforces the fact that our world consists of much more than the observable realm.

List of sources

Caygill, Howard. 1995. A Kant Dictionary. Oxford: Blackwell Publishing.
Greene, B. 2000. The Elegant Universe. London: Random House.
Jung, C. G. 1953-77. Collected Works of C. G. Jung, Vol 11. Edited by H. Read, Michael Fordham and Gerhard Adler. Translated by R. F. C. Hull. Princeton: Princeton University.
Jung, C. G. 1990. The Basic Writings of C. G. Jung. Translated by R. F. C. Hill. Selected and Introduced by V. S. de Laszlo. Princeton: Princeton University.
Kant, I. 1934. Critique of Pure Reason. Translated by J. M. D. Meiklejohn. New York: Everyman’s Library.
Kant, I. 1997. Critique of Practical Reason. Translated by Mary Gregor. Introduction by Andrews Reath. Cambridge: Cambridge University.
Kugler, P. 2008. “Psychic imaging: a bridge between subject and object”, in The Cambridge Companion to Jung (Second Edition). Edited by Polly Young-Eisendrath and Terence Dawson. Cambridge: Cambridge University.
Ostenfeld, E. N. 1982. Forms, Matter and Mind. London: Marinus Nijhoff.
Pine, R. C. 2006. Science and the human prospect. Internet: http//
Tarnas, R. 1991. The Passion of the Western Mind: Understanding the Ideas that have shaped our worldview. New York: Ballantine.
Ward, A. 2006. Kant. The Three Critiques. Cambridge: Polity Press.

Author: Dr Willie Mc Loud (Ref.

Read also:
Kant, Noumena and Quantum Physics (Introduction)
Published in Contemporary Studies in Kantian Philosophy 3 (2018)

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