The ancients believed in an invisible world in which spirits and gods are to be found. In the Judeo-Christian tradition, this is referred to as the spirit world. The concept entered philosophical tradition with Plato, who reworked it into his intelligible world of forms. Later, the philosopher Immanuel Kant also incorporated a "noumenal realm" in his philosophy. With the strong accentuation of the rational in the Platonic-Kantian tradition, something that the ancients affirmed was lost, namely the possibility of having an intuition of that world. Once this happened, the noumenal realm became nothing more than an idea - a realm beyond experience that religious people believe in. Something that the sceptical scientific mind could not accommodate. But with new developments in theoretical physics the possibility arises that the ancients could have been right after all.
Since early times peoples from all over the world believed that an invisible world exists next to our own visible world. They believed that that world is occupied by gods and spirits. It was typically referred to as the "other world" and cosmic domains like heaven (as the abode of the gods) and the underworld were believed to be situated in that world. We find reference to it in the earliest writings of people like the Sumerians and the Egyptians. In fact, it seems that all ancient peoples held the belief that such a world exists. The Greeks and Hebrews also believed in it - their views played a formative role in the Judeo-Christian conception of the spirit world. The ancients even believed that we have some type of intuition directed to that world.
The idea of such an invisible world had a great impact on the thinking of the Greek philosopher Plato (5th to 4th century BC). In fact, his idea of a "world of forms (or ideas)" originated from the age-old belief in an invisible world. In Plato, the invisible world of the ancients is reworked into an intelligible world - a world that is only accessible through thought. He distinguished between the visible world of our senses and the intelligible world. Although he believed that that world is only accessible through thought, he nevertheless still held that it is a (the only) real world.
Later generations of philosophers followed Plato's lead in discerning an intelligible or noumenal world (from the Greek word "nous", meaning mind). The greatest of them was the philosopher Immanuel Kant (1724-1804). The idea of a noumenal world differing from the phenomenal world featured prominently in his philosophy. Although he rejected the Platonic idea that we could access that world in thought (he rejected the possibility of humans having an "intelligible intuition" thereof), he still held that we can think it. But, according to Kant, we can have no "knowledge" of that world. This, however, did not stop him from thinking that such a world could really exist - he envisioned it as underlying and giving form to the phenomenal world.
The Platonic move to envision the invisible world as an intelligible world eventually had the opposite outcome that he intended - it led to the rejection of the possibility that such a world exists. How did it happen? Once the possibility of having any intuition (that is, a sensing without the use of rational processes, an immediate awareness) of that world was rejected (in Kant), it became nothing more than a mere idea - an idea of something beyond the senses that religious people "believe" in. Since nothing in science gave the slightest reason to believe in such a world, a general consensus developed that such a world does not exist.
But was Kant right? Do we not have any intuition of a noumenal world? Such an intuition would imply some type of experience of that world - which is in fact what the ancients affirmed. What is more, theoretical physics now also envisions a world very much in accordance with the Kantian idea of the noumenal world - but one that is real and which could in principle be accessible in some kind of experience.
Plato's intelligible world
Why did Plato redefine the invisible world as an intelligible world? The reason is simple. Socrates, Plato's teacher "discovered" reason. This led to one of the most important shifts to ever occur in Western thought - the accentuation of reason as the most important of all human faculties. It dawned on these men that reason is what makes us distinctly human (animals cannot reason). We can even through reason control our animal passions (therefore reason guides us to the virtuous life). In Plato's opinion, the human mind ("nous") should be viewed as a thinking ability - he equated it with intelligence. This ability is seated in the human soul, that part of humans through which they have access to the invisible world. Therefore that world - the one that is accessible only through thought - is to be understood as an intelligible world.
This Platonic move - to equate the invisible world with the intelligible - is clearly observable in his Phaedo. In the dialogues between Socrates and his friends, it is mentioned that he takes the view of the mystics (the Orphics), in which the invisible world played an important part, as the point of departure (as a "metaphor") for his own view. Two different worlds are distinguished, namely the invisible and the visible realm. The invisible realm is called "the realm of the absolute, constant and invariable" whereas the visible world is always changing. In this last respect, Plato follows Parmenides of Elea (b. c515 BC) who argued for two worlds, one that is the real world and which is eternal, indivisible, motionless and changeless and the other that is the world of our senses, which is a world of "appearances". Plato furthermore distinguished two types of things which belong to these two different worlds, namely the invisible (the forms) and the visible things.
According to the dialogues in the Phaedo the soul belongs to the invisible world: "Since the soul is invisible, it belongs to the eternal invisible world... When it [the soul] investigates by itself, it passes into the realm of the pure and everlasting and changeless; and being of a kindred nature, when it is once independent and free from interference, consorts with it". True contemplation is not with the eyes, but with the soul - or, more precisely, with the intellect. In this regard, we read: "We are in fact convinced that if we are ever to have pure knowledge of anything, we must get rid of the body and contemplate things by themselves [i.e. as they really are] with the soul by itself" and "the man who pursues the truth by applying his pure and unadulterated thought to the pure and unadulterated object... Is not this the person, Simmias, who will reach the goal of reality, if anybody can?".
In Plato's writings, the human mind (nous) has a direct intuitive understanding of the invisible realm. Again this view goes back to Parmenides who argued for a dualism wherein nous describes an intellectual perception, which should be distinguished from sense perception. But was this how the earlier Greeks, in general, viewed the mind? As mentioned in the Oxford dictionary, the Greek word nous meant "mind, intelligence, intuitive apprehension". Although the Greeks allocated both understanding and intuition in the mind, there is no reason to believe that they viewed the intuition directed to the invisible world solely as an "intellectual" intuition (this view originated with Parmenides).
It seems that the Greeks allowed for a direct intuitive awareness of the invisible world, which is only then (as a secondary move) brought to understanding. The Pythagoreans, for example, seem to have held the opinion that we have some intuition of that world in the deepest essence of our being and that our thinking (even in reference to that intuition) is only secondary. They distinguished between 1) the higher soul, seat of the intuitive mind, 2) the rational soul, the seat of discursive reason and 3) the non-rational soul, responsible for the senses, appetites and motion. Even Plato often refers to a perception of the invisible world (for example, through the "eye" of the soul) which seems to be more fundamental than the thought thereof (why use the metaphor of "eye" if it is in fact the act of thinking that should be accentuated). The overall move in Plato's philosophy - and the Western philosophical tradition derived from him - was, however, to collapse the noumenal into the intelligible.
Plato's opinion on the relation between the worlds changed through the course of his writing. At first (in the Phaedo) the "invisible world" is viewed as a separate domain where human souls go between lives (and where the gods live), but in the Republic the "intelligible" world (as it is now called) is more closely connected to our own world (we can see that in the metaphor of the cave). This (our) world is somehow dependent on the real world for its existence (where the forms for the phenomena in this world is situated). In the Timaeus, the real world (of unchanging being where the forms are situated) underlies this world (of becoming) in a very real sense in that it gives form to it.
Kant's noumenal world
Kant lived many centuries after Plato but his reworking of the Platonic position produced one of the most important philosophical traditions since Plato. He lived during the height of the modern epoch - also known as the age of reason. Not only was reason accentuated more than ever before (in accordance with the Platonic-Aristotelian tradition), the discovery of empirical science demonstrated the practical possibilities of reason in a powerful way. And in science the sole focus is on the world of the senses. This now became the "real world". But even in the face of this new focus on the sensible world, Kant stood his ground in affirming the possibility of the "noumenal world". Kant was a Christian and believed in the existence of a spiritual world. And following Plato, he distinguished between the sensible (phenomenal) world and the "intelligible world", also called a "noumenal" world (which for Kant is supra-sensible, i.e. transcending sensible experience).
Kant's most important work, The Critique of Pure Reason, focuses (in the spirit of the age) first of all on our interaction with the sensible world (in contrast with Plato's focus on our interaction with the intelligible world). He shows how human thinking and sensing are interacting to establish "knowledge" of the sensible world. For Kant, the only knowledge possible is of this (sensible) world. He rejects the Platonic position that we can have any knowledge of the noumenal world. But this does not stop us from thinking the noumenal realm. The Critique distinguishes between the human faculty of "understanding" which get its content from the senses and "reason" which is quite independent of the sensible world and can think intelligible things. But Kant's goal with this work is to establish the limits of what reason can achieve.
Although Kant mentions that direct "intelligible intuitions" of the noumenal world is in principle possible, he argues that this is not something that humans have (God can have them). We can ask: But why didn't he allow for possible intuitions of the noumenal world other than intelligible ones? The reason for this is possibly because Kant was influenced by the Platonic move to view all intuitions of the noumenal world as intelligible ones. Kant's distinction between the sensible and intelligible (supra-sensible, noumenal) worlds therefore also incorporates a dichotomy between experience and intelligence. Kant assumes that all experience is sensible. He did not allow (as many ancient peoples seem to have done) for the possibility of an inner non-sensible experience directed to the noumenal realm. Although he did not exclude such noumenal intuitions in principle, he thought that we are not acquainted with such intuitions. He writes in the Critique of Pure Reason in a section called "Phenomena and Noumena": "room thus remains for some other sort of intuition... [but] we are acquainted with no sort of intuition other than our own sensible one" (B343).
As far as our understanding is concerned (to the extent that it is directed to the sensible world), the noumenal world is "empty" - we cannot gain any knowledge thereof. As far as reason is concerned, however, we can use reason, especially "practical reason", to argue for certain things about the noumenal realm. Starting with the Critique of Pure Reason, and developing his ideas further in his other two Critiques (of practical reason and the power of judgement), Kant developed an extensive view of the noumenal world. In the second Critique, he argued that we need the noumenal realm to account for our moral nature, our ability to make moral laws and act according to them. In the last Critique, Kant takes the noumenal world as the ultimate ground for our world, being ultimately responsible for the design of the whole spatio-temporal world. In this, he follows Plato in the Timaeus. Kant's noumenal realm is the supra-sensible ground of all phenomena, wherein the form-giving dynamic spontaneity (freedom) which gives form to the phenomenal world, is situated. Humans as well as nature are grounded and partially situated in the noumenal realm.
Science and the noumenal world
Towards the end of the modern epoch the Kantian affirmation of the existence of a noumenal realm seemed to be superficial. How can we ever show the existence of a realm of which we cannot have any experience. It's like defining something in such a way that it is beyond experimental proof and then affirming its existence in accordance with your Christian view. For the modern mind, which was so smitten by the power of reason, and who believed that science can give all the answers, this seems to be an excuse to keep believing in the face of scientific discovery - which seemed to confirm that the world is nothing more than the sensible world. Therefore a consensus developed that such a world could not exist.
Those days are, however, long gone. Gone is the days when it was believed that the human capacity to solve all problems and ultimately understand everything was around the corner. The centuries during which scientists affirmed that they would be able to understand everything in the not-too-distant future has lead to a new consensus (even though many scientists still hold to the modernist view), namely that this view should be taken with a pinch of salt. The world is extremely complex. More complex than modern man could ever have imagined. Today, scientists except ideas that were frowned upon only a few years ago, for example, that dark matter and dark energy exist. In their efforts to develop an unified theory that could integrate all the basic forces of nature, theoretical physicists are even postulating the existence of a higher dimensional realm that are interwoven with our own three dimensional sensible world. Scientists are confronted with the fact that it might just be possible that we would never be able to fully fathom what reality is like.
This development is in accordance with the position of some existential philosophers who rejected the modern efforts to establish reason as the sole arbiter of existence. Some like Friedrich Nietzsche (1844-1900), developed an anti-Platonic, anti-Kantian position. He argued that we should affirm our earthly existence and embrace our inner drives - we must not bow to reason and fight against our true nature. In his opinion, all talk of another or noumenal world is the result of mankind's (especially religious people's) inability to cope with the here and now. They cannot cope in this world - and therefore developed the idea of another world where they would be happy. The post-modern philosophers took Nietzsche's views as the point of departure to develop an anti-modernist perspective in matters concerning the nature of morality, truth and reality. Other philosophers like Søren Kierkegaard (1813-1855) followed a different route - he rejected the efforts to fathom all of existence through reason. He affirmed the reality of the Christian experience even in the face of reason's onslaught on the supernatural. In a sense, he rejected all efforts to reasonably establish the ground for the Christian faith (and our experience of the spiritual).
What I propose is that although we cannot reject reason's ability to fathom existence, we should at the same time affirm it's reductionist nature. In it's efforts to understand reality, reason has to construct models, establish approximations, formulate reductionist concepts. This is in fact what the Copenhagen interpretation confirmed for quantum physics - we can only have a partial concept of the reality that we study. This is where Plato and Kant have fallen short - in their efforts to rework the invisible (spiritual) realm as an intelligible realm, they have been reductionist. They have not been able to sufficiently account for those intuitions of that realm that the ancients, and many religious people throughout the ages, have affirmed to exist. Kant excluded the possibility of such intuitions in his philosophy - even though it is possible (in my opinion) to incorporate it therein. For him, all experience is sensible - but what about the possibility of non-sensible (or supra-sensible) experience of the noumenal?
In spite of this, Kant's conceptualization of the noumenal realm shows remarkable agreement with the higher dimensional structure of the universe that theoretical physicists postulate. These dimensions are very small and not accessible to our senses - they are supra-sensible. But they are interwoven in the structure of space. They underlay the phemonenal world as the form-giving part of the cosmos. All nature are in some way grounded therein - also are we as humans. Although most particle-structures could have parts in both realms, it is in principle possible that at least some particle-structures exist solely in that realm, implying the possibility of a whole world unknown to our senses existing next to our own without us knowing it. It is possible that humans have a part situated in higher dimensions (corresponding to what has traditionally been called the soul or spirit) that co-exists with our physical bodies. This description does not only closely agree with Kant's ideas about the noumenal realm, they affirm the possibility of a real spiritual world.
During the modern epoch, people thought that they have finally arrived and that the ancients were primitive and without true knowledge. In our day there is a new appreciation for the views of those people. They experienced something about the world that the rational mindset has conditioned us to reject as something unreal. They believed in some type of intuition directed towards that world that religious people from all around the world has continued to confirm in their everyday experience (not only Christians; there is no reason from a Christian point of view, why other religious experiences are not also directed to the spiritual world). One of the reasons why so many religious people have never bought into the modernist framework is because their own experience proved the opposite. Although many scientists are eager to (again in a reductionist way) ascribe all such experience to people's psychology, most Christians, for example, have a subtle, but distinct, awareness that their experience of God goes beyond themselves.
The one thing about the noumenal world that is especially interesting, is that Kant's formulation thereof corresponds so closely with scientific notions about a higher dimensional realm that co-exists with our own. It seems that through pure reason he was able to in a remarkable way foresee the eventual scientific formulation of models that describes the world as much more than a sensible world. Although this could (once proven) confirm the power of reason, his philosophy at the same time should always remind us how reductionist reason is. We should use reason, but we should also trust our deepest spiritual intuitions about our own experience in the world. Both reason and such intuition should be our guides in this world. Without such intuition, humankind will wander as a person in the dark, groping towards a destiny without hope.
Author: Dr Willie Mc Loud (Ref. www.wmcloud.blogspot.com)
The God Impulse (life after death?)
Kant's noumenal realm reconsidered in the light of contemporary developments in physics