Théodora Domenech
The Idea of Phenomenon

First and foremost, the idea of phenomenon seems banal and in no way controversial. It is a matter of defining what a phenomenon is, or of studying the definitions that different authors throughout the history of philosophy have proposed. But if we examine it more closely, we notice that the terms of “idea” and “phenomenon” designate two distinct orders of reality that are opposites in certain aspects. For instance, we commonly understand “phenomenon” as being something perceptible, and therefore sensible and singular. The word “idea,” however, refers to a regulated intellectual activity, of a universal or at least general character. Thus, one cannot connect the terms “idea” and “phenomenon” together without first interrogating in a most profound way what relationship these two concepts have in the History of thoughts.

In fact, if the phenomenon and the idea both require two distinct – or opposing – human faculties, one might ask if the task of “defining” – that is to say making the “phenomenon” rationally explicit, rather than directly perceiving it, is not doomed to necessarily “miss” its object. The “idea” would be definable, but the phenomenon would not, since the latter is only “perceptible.” The purpose of my conference is not to devalue the task of defining phenomena, thus making it impossible. However, we must ask ourselves in exactly what paradigm does this definition of phenomenon not apply to contradictions. Why would phenomena necessarily be irrational? Why should the term “idea” be associated with rationality? And what if the “idea” is considered to be a phenomenon? Using the different definitions of the phenomena on the one hand and of the idea on the other, we will analyze three possible modalities of the relationship between both of these terms. We will first study their radical heterogeneity, as suggested in Plato and Aristotle’s critiques of Protagoras’s thought. A phenomenon is, according to them, both idea-less and indefinable. Later, we will study their complementarity as did Kant through the distinction he established between noumenon and phenomenon. For him, the “idea” connected to reality. And, even though the phenomenon may be definable, the idea is not. Lastly, we will turn to their homogeneity, principally put forward by Hegel and present in Husserlian phenomenology, both wishing to go beyond the opposition between idea and phenomenon.


The notion of phenomenon is believed to have been born with Protagoras, around 5th century BC –  although a scrupulous historian would point out that none of his texts have survived, and that all we have are quotations told by other authors. Among them, Plato and Aristotle who quoted his most famous maxim “Man is the measure of all things”. However, they both heavily criticized it, and Protagoras’ thinking was associated with material “phenomenalism”, according to which knowledge can only exist within perception. It therefore follows that there is no being but in appearances. We will try to discern what this philosophy entails and also attempt to understand why it was so harshly condemned.

Theaetetus [1] [151e-152a]: 

Socrates: Perception, you say, is knowledge?

Theaetetus : Yes.

Soc : And, indeed, if I may venture to say so, it is not a bad description of knowledge that you have given, but one which Protagoras also used to give. Only, he has said the same thing in a different way. For he says somewhere that man is “the measure of all things, of the existence of the things that are and the non-existence of the things that are not”. You have read that, I suppose?

Th : Yes, I have read of it often.

Soc : Well, is not this about what he means, that individual things are for me as they appear to me, and for you in turn such as they appear to you – you and I being “man”?

Cratylus [2] [385e-386a]: 

Socrates: Now, Hermogenes, let us see. Do you think this is true of the real things, that their reality is a separate one for each person, as Protagoras said with his doctrine that man is the measure of all things – that things are to me such as they seem to me, and to you such as they seem to you – or do you think things have some fixed reality of their own?

In these few lines we can picture a portrait of the Protagorean thought, in which the problem of “measure” (i.e., knowledge) and “phenomenon” are joined. We could summarize it in three points: 1) knowledge is nothing but perception, 2) the measure of things is relative to mankind, 3) things are “for me” or “for you”; in other words, the being of things is relative to mankind (there is no autonomous thing).  

We can therefore find three consequences that are potentially harmful, according to Plato: 1) the soul or the mind alone are incapable of knowing truth, 2) truth is relative and ephemeral 3) things do not have their own identity (which is the most controversial point). 

Plato pursues the dialogue with an example: the perception of wind. If knowledge resides in perception, declares Socrates, then the wind can be both cold and hot; cold according to me, hot according to you. Each time one attributes a property to the wind, there will always be a need to give precisions on the context; things would never have their own properties, so that it would even be arbitrary to still talk about the “wind” as if it had an unequivocal identity. This according to Socrates therefore leads Protagorean thought directly to the Heraclitean conception according to which reality forms a protean whole in progress; a kind of matrix that is perpetually changing. Fire is the principle of all things claimed Heraclitus, because fire takes all possible shapes, unites opposites, is constanly in movement, etc. There are no Things, meaning no separate entities.

Plato reaches the conclusion that refusing the privilege of the mind over perception, as well as the existence of “ideas” which are “behind appearances” – as is the case with the Protagorean concept of the “phenomenon” – amounts to a refusal of the principle of reality. Phenomena only lead to an illusionary world.  

This critique is quite different from Aristotle’s, who criticizes the Platonic ontological position. It places itself on an epistemological level, leaving aside questions relative to the nature of reality. Phenomenon is opposed to rationality more than to reality. 

Metaphysics [3] [Γ 5, 1009 a – 5-15]3 : 

“From the same view proceeds the theory of Protagoras, and both alike must be either true or false. For it, all opinions and appearances are true, everything must be at once true and false; because many people form judgments which are opposite to those of others, and imagine that those who do not think the same as themselves are wrong: hence the same thing must both be and not be. And if this is so, all opinions must be true; for those who are wrong and those who are right think contrarily to each other. So if reality is of this nature, everyone will be right”.

The vocabulary employed by Aristotle places the debate under the register of truth and falseness of judgment. The common thread of the whole is the possibility of founding stable knowledge. He attributes the role of establishing a “truth criterion” to philosophy, one that splits singular perceptions into true and false ones. Philosophy is characterized by the search of an unequivocal meaning regarding the world we perceive. This is why the phenomenalist posture assigned to Protagoras is outright rejected and considered to be a vain exchange of subjective opinions. 

Instead of the phenomenon itself, it is the phenomenalist reduction that is condemned in these two critiques. This thought gives more importance to singular perception than the universal significance of the mind. 

The stakes would have been completely different if the “limits” of the phenomenon had not been restrained in the sphere of the purely sensorial or irrational opinion. 

Thus, while keeping the same conception of philosophy as Aristotle – i.e., as a rational investigation, a founding base of all particular knowledge – the term of “phenomenon” returns in Kant’s writing in a far more positive light. It is no longer opposed to rationality – on the contrary, a phenomenon is what appears to a subject in a rational way. It is a representation that is structured by rational categories. Only then is the expression “idea of phenomenon” split into two possible meanings. It depends on what the term “idea” refers to: rationality or reality? 


For both Plato and Aristotle, philosophy consists in going beyond solely subjective appearances to attain an object beyond all phenomenality, whereas for Kant, phenomena are the only accessible things. Something might exist behind appearances, but this will remain out of the field of possible knowledge. It therefore follows that: 1) phenomena are rational, 2) what Plato called “the fixed reality of things” – therefore, the idea – is (paradoxically) irrational, 3) the criteria of knowledge can only be found in the subjective structure of our representations. 

With Kant, phenomenon becomes the very center of rationality. For him, philosophy consists in questioning how meaning is constituted and how the faculties of the mind and of sensibility articulate together. For Kant, we cannot perceive something without spontaneously giving a rational shape to the information received by sensitive impressions. Everything comes together. We do not perceive something, then interpret it in a rational way. Perception is immediately and rationally structured. 

We now have to explain how phenomenon, which still is dependent on individual sensations, can be the basis of knowledge. If Plato and Aristotle were unable to find any universal significance to phenomenon because of its individual dimension, Kant points it out. He manages to find this universality by disregarding the phenomenon’s content to only interrogate its different forms.   

Let us go back to the example given by Socrates. If we limit ourselves to simple perception, we obtain two contradictory assertions. The wind is cold and hot ; cold to me and hot to you. Insofar as the wind has no properties of its own, there is no way to decide if one assertion is true, the other false. Therefore, Plato’s conclusions were 1) every perception is relative, and 2) we cannot reach what the wind “is” / its “idea”. Kant finds a way to get round the first assertion by creating a distinction between form and content. What is relative in perception only concerns its content. He then invites us to disregard the particular content of both judgments and focus on their “forms”. The form of judgment designates the way in which my physical sensations are articulated, how they express themselves through conceptual language and the manner in which I return a verdict expressed under a propositional form like “the wind is hot”. By regarding this process  – where both judgments have the same form – the contradictions disappear along with the individual dimension of these judgments. Perception is no longer relative. But a question remains: what does Kant do with the second assertion? What about the reality of the wind? The wind “as it is,” independently of subjective perception? Here, we should distinguish idea from rationality. Kant inherits Plato’s conception of the Idea; a conception of a hidden reality from which phenomenon is only the “sign” (like the tip of an iceberg). 

Critique of Pure Reason [4], Preface [BXXVI-XXVII] :

« we can have cognition of no object as a thing in itself (…). Yet the reservation must also be well noted, that even if we cannot cognize the same objects as things in themselves, we at least must be able to think them as things in themselves. For otherwise there would follow the absurd proposition that there is an appearance without anything that appears»

[5] [A 288-289]

“If we want to call this object a noumenon because the representation of it is nothing sensible, we are free to do so. But since we cannot apply any of our concepts of the understanding to it, this representation still remains empty for us, and serves for nothing but to designate the boundaries of our sensible cognition and leave open a space that we can fill up neither through possible experience nor through the pure understanding” 

The way Kant insists on the necessity to maintain the existence of a thing “in-itself”, of a “noumenon”, shows that Kant’s thought – while emphasizing the phenomenon – cannot be considered a phenomenalism. This noumenon – independent from subjectivity – has for sole purpose to limit our purely mental constructions. It imposes a certain framework on thought. Here, Kant takes a step back from the Protagorean maxim. If, indeed, man gives the measure of the phenomenon, this measure must be “limited” by a non-subjective entity. 

Kant has been blamed for having affirmed the existence of an “other world”. Despite the fact that he insists rather on the necessity – for knowledge – to postulate the existence of other founding principles than the knowing subject, it remains true that phenomenon and “idea” understood as “noumenon” belong to radically separate spheres. What if they were not separated at all?   


“who is it really who tells us that the apparent world must be of less value than the true one?” writes Nietzsche in Will to Power [6]. The simple distinction between two worlds is perceived by him as a symptom of decadence, of boredom; this dualism betraying a human too human sentiment to denigrate the world and to desire to flee it : “we take revenge on life, with a phantasmagoria of “another,” a “better” life” [7]. 

By the rejection of any “underworld”, Nietzsche invites us – not to replace the apparent with being – but to have a perspective “beyond” the one and the other; one has to “unlearn our antinomies”. His thought is then based on a vitalist phenomenism. 

Vitalism will not help us to keep our initial goal, being to conjunctively think of “idea” and “phenomenon”. But it is not the only way to have a perspective “behind” the opposition between being and appearance. The idealist thinkers also wanted to “unlearn” the opposition. Among them – and the most representative of them all – is Hegel. For him phenomenon is not the appearance of something separate from the subject’s consciousness ; it is solely consciousness that takes different shapes depending on its type of thought. Rationality is therefore not only relative to the relationship between a subject and its world. Rationality, as having part in an act of consciousness, is inherent to the world. We face here a spiritual monism, i.e., spiritual phenomenalism.

Hegel formulates the alternative in these words: either I define the world as independent from subjective activity, or I consider both of them to be as relative to one another. He does not ask if the things “exist” or not. He rather interrogates rational judgment. His question is: was happens when I think a world exists? What kind of thought is that? A kind of thought defined by Hegel as the “negative” moment of the mind, when one pretends there are things existing separately from the mind, and the subject denies its proper act of consciousness. Even when he pretends to be in front of material objects, the objects are nothing but “thought” contained in his mind. By doing this, by granting existence to the Thing, one only “reifies” the mind. This self-exit or self-negation is described as the first stage of thought. The second being a self-consciousness. The subject goes to a consciousness of things to a consciousness of himself thinking those things. He then, in this second moment, questions the rational faculties and their role in perception (the “Kant” moment). Both moments – in other words, where I first assign an independent existence to things, then I discover the relationship between things and thought – is then followed by a third one : I realise that all of reality is nothing but the deployment of different expression modalities of the mind. Phenomenon does not designate the appearance of something exterior – a world, things – but the appearance of the Spirit to himself. The Spirit phenomenalizes itself. 

For the first time, phenomenon is described as the only reality, not as an illusory experience nor a strict subjective representation. There is therefore no underworld. The world is not phenomenon for consciousness: it is also in-itself.

However this spiritual monism does not lead to logical rationalism, which is limited to a part of the Spirit’s process. Even when Hegel claims that “the Real is rational, the rational is real “, it refers to Spirit as a general movement of manifestation. Hegel therefore includes – as if they were two “moments” – being and appearing, subjective and objective facts, which are supposed to exclude one another in static formal logic.

Hegel wrote the first “phenomenology” that was remembered in philosophical tradition. And yet the phenomenological movement – born in the beginning of the 20th century – has refused any affiliation to his thought. Maldiney [8] addressed him a critique, affirming that Hegel began “on faulty ground” identifying the essence of the world with its signification. This kind of argument or philosophical stance already existed in Hegel’s time; we find it in all “Rousseauist” thought. The idea of a natural state preceding language, preceding cultural norms etc. is much closer to the phenomenologists that call for an originary experience preceding the activity of thought. While this “natural” Rousseauist state – and by extension, this originary experience of the flesh –  is for Hegel nothing but a utopia: the world is permanently invested and full of significations. There is no experience originating from what utterly exceeds all representation.

Paradoxically, Maldiney’s critique is also valid for the father of phenomenology. Husserl’s analysis of the mind’s structure is also an analysis of the things “as they are”. Through this, he wishes to consider the content of thought as part of reality and not to restrain it to being a mere subjective image of it. The Husserlian maxim – a maxim shared by all phenomenologists – “back to the things themselves” is based on the principle that the thing as it is in-itself is “given” / “present” in my conscience. Defining the very being of things as signification appears to be unavoidable if we want to get beyond Kant’s dualism between the things as-they-are and the images of the things present in my thought. In this paradigm, the “idea” is the very essence of phenomenon. 


To speak of “an idea of phenomenon” supposes that ideality and phenomenality are not mutually excluded but, on the contrary, united. Without this – as we saw with the “phenomenalism” criticized by Plato and Aristotle – the Phenomenon is, by definition, both unstable and undefinable. For most post-Husserlian phenomenologists, and for some contemporary authors situated in the tradition of Nietzsche – i.e., vitalists, or more generally “irrationalists” – the “idea of phenomenon” is nothing but what Wittgenstein would call a “misplaced question”. I have tried to put forward the way in which the principal modern idealists have strived to go beyond the opposition of both terms.

We have seen that, for Kant, phenomenon is the very locus of the exercise of reason. But this validation proceeds from an existence postulate of a hidden spiritual reality – an idealistic and unknowable “underworld” that has been strongly criticized by Nietzsche. However, despite this critique, by facing other realms of knowledge (notably sciences), a great number of authors who claim the irrationality of the world are once again forced to separate a knowable realm and an unknowable realm. We finally find the same dichotomy and the same denigration of appearances – while this time the denigration concerns rational appearing. So if we want to think of the “phenomenon idea” in depth, that is to say that we believe things have a meaning one can discover – this “meaning” not being an artificial elaboration of thought, but something held by the world itself – I find it interesting to turn towards the idealistic thinkers who are too-often neglected and look at how to “update” them.   


[1] Plato, VII, trans. H.N. Fowler, Loeb Classical Library, Cambridge : Harvard Univ Press, 1921, 1987, p. 40.
[2] Plato, IV, trans. H.N. Fowler, Loeb Classical Library, Cambridge : Harvard Univ Press, 1926, 1992, p. 15.
[3] Aristotle in 23 Volumes, Vols.17, 18, trans. Hugh Tredennick. Cambridge, MA, Harvard Univ Press; London, William Heinemann Ltd. 1933, 1989, p. 181-183.
[4], [5] Immanuel Kant, Critique of Pure Reason, trans. Paul Guyer, Allen W. Wood, Cambridge University Press, 2000, p. 115 and p. 381.
[6] Friedrich Nietzsche, The Will to Power, trans. Walter Kaufmann and R.J. Hollingdale, Random House, New York, 1967, p. 321, 586B.
[7] Friedrich Nietzsche, Twilight of the Idoles, III.6, in : The works of Friedrich Nietsche, trans. Thomas Commun, London 1899 p. 122.
[8] Henri Maldiney, Regard, Parole, Espace, “La méconnaissance du Sentir et de la Première Parole ou le Faux Départ de la Phénoménologie de Hegel”, p. 254-321.