How Can Thought Grasp Reality Without Reducing It to Our Concepts? Plato, Kant, and Adorno on the Limits of Conceptual Thought
We understand the world through concepts. We describe someone as a worker, a citizen, or an individual, and these categories allow us to identify characteristics that might otherwise remain difficult to grasp. Yet none of them captures everything that person is. A worker is not simply a position within an economic system, just as a citizen is not exhausted by the characteristics through which we identify them. Concepts make understanding possible, but they can also obscure the particularity of what they describe.
This raises a fundamental philosophical question: how can thought understand reality without reducing it to the concepts through which it becomes intelligible? Abandoning concepts altogether would make knowledge impossible, while assuming that they fully capture their objects risks confusing our understanding of things with the things themselves.
This tension runs through the history of philosophy, although it takes different forms in different thinkers. Plato examines the relationship between universal Forms and particular things, Kant investigates the conditions under which concepts can apply to sensible experience, and Adorno questions whether conceptual determination can ever exhaust its object.
2. Plato: The problem of participation
One of the earliest formulations of this problem appears in Plato's Parmenides. In the dialogue, the young Socrates defends the existence of Forms: universal realities such as Beauty itself, Justice itself, and Largeness itself, through which particular things can be understood as beautiful, just, or large. The Forms are supposed to explain what particular things have in common (Plato, 1997, 128e–130a).
Parmenides challenges Socrates to explain how this relationship actually works. What does it mean for a particular beautiful thing to participate in Beauty itself? Does it participate in the whole Form or only a part of it? If the whole Form is present in several things, how can it remain one and the same? If only a part is present in each thing, does the Form become divisible? These objections expose a difficulty in explaining participation: asserting that particular things derive their properties from universal Forms does not yet establish how the relationship between them works (Plato, 1997, 130e–131e).
The problem becomes especially apparent in the Third Man Argument. If a particular man and the Form of Man are both called men, their common character may require a further Form to explain it. That new Form, together with the original instances, may in turn require another Form, setting off an indefinite regress (Plato, 1997, 132a–b; Rickless, 2026).
The dialogue does not simply establish that Plato abandons the theory of Forms. Its later arguments explore the consequences of assuming that the One both is and is not, in a series of exercises whose overall philosophical purpose remains contested. The earlier criticisms nevertheless expose difficulties that any adequate account of the relationship between universal and particular must confront (Rickless, 2026).
This is where Plato's problem becomes relevant to the argument of this essay. A universal determination must somehow account for the particular things it is supposed to explain, yet the relationship between the two cannot simply be taken for granted. Kant approaches this difficulty from a different philosophical direction, asking what makes it possible for concepts to apply to sensible intuition and yield objective knowledge, rather than how sensible particulars participate in separate Forms.
3. Kant: The mediation of concept and intuition
In the Critique of Pure Reason, Immanuel Kant investigates the conditions under which knowledge is possible. A central distinction in his account is that between concepts of the understanding and sensible intuitions. Concepts allow us to think objects, while intuitions provide the sensible content through which objects are given to us. Neither, on its own, is sufficient for human knowledge (Kant, 1998, A50–51/B74–75).
This distinction raises a problem: how can pure concepts of the understanding, such as substance or causality, legitimately apply to sensible appearances? Kant addresses this question in his chapter on the schematism of the pure concepts of the understanding.
His answer is the transcendental schema, which mediates between categories and sensible intuition. A schema is a rule that makes the application of a category to appearances possible. For example, Kant characterises the schema of substance in terms of the permanence of the real in time. Although the properties of something may change, we can experience it as something that persists through those changes (Kant, 1998, A143–144/B183–184).
The schema thus explains how a pure concept can acquire application within sensible experience. It is not enough for the mind to possess concepts; there must also be an account of how those concepts relate to what is given in intuition.
Kant's account of schematism is not confined to transcendental schemas. Empirical concepts also have schemas: the concept of a dog, for example, involves a rule that allows the imagination to represent a four-footed animal in general, rather than any particular dog. The schema is not an image of an individual animal but a rule for representing different instances of the concept (Kant, 1998, A140–142/B179–181).
This distinction matters because the transcendental schematism of the pure categories addresses a more specific problem. It explains how concepts that do not originate in experience can nevertheless apply objectively to sensible appearances. Both empirical and transcendental schemas concern the relation between general concepts and particular instances, but only the latter explains how pure categories acquire application through temporal determination.
The transcendental schema should therefore not be understood as a third entity inserted between two otherwise separate domains. It is a rule of synthesis that relates a category to appearances through temporal determination. Kant's account is intended to explain how the conceptual and the sensible can cooperate in objective knowledge while remaining distinct.
Adorno's reading of Kant raises a further question. Even if Kant explains how categories can apply objectively to sensible appearances, does his account give sufficient weight to the object's contribution to knowledge? Or does it continue to privilege the conditions through which the subject makes the object intelligible? The issue extends beyond the application of pure concepts to experience. It concerns whether an account of the conditions of objective knowledge adequately recognises the object's capacity to resist the determinations through which it becomes intelligible.
4. Adorno: Non-identity and affinity
Adorno's critique of conceptual thought begins with the observation that concepts identify particular things by subsuming them under general determinations. Such identification is indispensable: without concepts, we could not recognise, compare, or understand objects. Yet identifying an object through a concept does not guarantee that we have captured everything it is. Adorno calls attention to this difference through the idea of non-identity: the object exceeds the conceptual determinations through which it becomes intelligible (Adorno, 1973, pp. 5–6).
Consider the classification of someone as a worker. This concept can disclose important aspects of that person's social and economic position, yet it cannot encompass the entirety of their experiences, relationships, history, and possibilities. The classification may be valid without being exhaustive. For Adorno, identity thinking names the tendency to treat such a determination as if it provided a complete account of the object, overlooking whatever does not fit within the established concept.
How, then, can concepts relate to objects without reducing them to conceptual identities? The notion of affinity can help describe this possibility, provided it is not understood as a separate mechanism that guarantees harmony between thought and reality. Concepts can illuminate an object while remaining responsive to its particularity, and an encounter with that object may reveal limitations in the concepts through which we initially approached it. The resulting criticism remains conceptual: rather than abandoning a concept or seeking direct access to something beyond thought, we reconsider the object in the light of what our established determination fails to capture.
This also clarifies Adorno's relation to Kant. Kant asks how pure categories can apply objectively to sensible appearances; Adorno questions whether the conditions through which the subject makes an object intelligible can adequately recognise the object's non-identity with those determinations. His emphasis on the priority of the object challenges the assumption that the subject's role in constituting objective experience gives it the authority to determine the object completely. At a broader level, their disagreement recalls the traditional dispute between idealism and materialism over the relation between consciousness and material reality, now focused on how the subject's contribution to knowledge relates to the object's resistance to conceptual determination. (Adorno, 1973, pp. 183–197; Pickford & Zuidervaart, 2024).
Adorno's position is not a simple reversal in which Kant privileges the subject while Adorno grants the object complete independence. The object is not an untouched reality standing outside every form of mediation, since the subject itself is materially and historically constituted. Rather, Adorno challenges the priority accorded to a constitutive subject whose conceptual activity risks treating its own determinations as exhaustive accounts of what exists.
Non-identity becomes recognisable through the critical examination of particular identifications, when what a concept claims about an object conflicts with what the object reveals. Thought need not abandon the concept; it must recognise its limits and reconsider the object in the light of what the concept leaves out. This process does not overcome mediation but makes its limitations available for criticism.
Adorno thus transforms the problem he inherits from Kant. The question concerns not only how thought can know objects, but how it can remain responsive to what its own conceptual activity fails to capture. His aim is to preserve the possibility of knowledge while resisting the assumption that conceptual identification can achieve complete mastery of its objects.
Conclusion
The problem of how thought relates to reality cannot be resolved simply by explaining how concepts apply to appearances or by assuming that concepts transparently reproduce what exists. Plato exposes the difficulty of explaining the relationship between universal Forms and particular things. Kant investigates the conditions under which concepts can apply objectively to sensible experience. Adorno takes up the problem of conceptual mediation while questioning whether an object's conceptual determination can ever exhaust what it is.
These approaches do not offer a single solution. Rather, they illuminate different dimensions of a persistent tension: concepts are necessary for understanding, yet their necessity does not guarantee their completeness. Kant explains the conditions under which objective knowledge is possible; Adorno asks how thought can recognise the limits of its conceptual determinations while preserving the possibility of knowledge.
The challenge is to understand how thought can remain responsive to what it seeks to know, including whatever resists its established categories. How can we think what exceeds our concepts without turning that excess into yet another concept that claims to exhaust it?
References
Adorno, T. W. (1973). Negative dialectics (E. B. Ashton, Trans.). Seabury Press. (Original work published 1966)
Kant, I. (1998). Critique of pure reason (P. Guyer & A. W. Wood, Trans. & Eds.). Cambridge University Press. (Original work published 1781/1787)
Pickford, H., & Zuidervaart, L. (2024). Theodor W. Adorno. In E. N. Zalta & U. Nodelman (Eds.), The Stanford Encyclopedia of Philosophy (Winter 2024 ed.). Metaphysics Research Lab, Stanford University. https://plato.stanford.edu/archives/win2024/entries/adorno/
Plato. (1997). Parmenides (M. L. Gill & P. Ryan, Trans.). In J. M. Cooper (Ed.), Plato: Complete works (pp. 359–397). Hackett Publishing Company.
Rickless, S. (2026). Plato's Parmenides. In E. N. Zalta & U. Nodelman (Eds.), The Stanford Encyclopedia of Philosophy (Spring 2026 ed.). Metaphysics Research Lab, Stanford University. https://plato.stanford.edu/archives/spr2026/entries/plato-parmenides/
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