What the Concept Leaves Out: Nietzsche and Adorno on the Limits of Knowledge
“Every concept arises from the equation of unequal things.”
— Friedrich Nietzsche, On Truth and Lying in a Non-Moral Sense
Consider two leaves lying on a table. One is broad and green, its edges sharply serrated; the other is smaller, yellowing, and partly torn. Their differences are immediately visible, yet we recognise both as leaves. The word allows us to treat them as instances of a familiar kind without first describing each one in detail. It helps us orient ourselves in the world, compare objects, and communicate with others. Without the ability to identify recurring kinds, ordinary thought would be difficult to imagine.
The differences between the leaves do not prevent us from applying the same word to both. The concept tells us what kind of thing each is, but says little about what distinguishes either one. It leaves out the pattern of its veins, the marks on its surface, and the circumstances in which it has grown. We can identify something correctly while remaining ignorant of much that makes it particular. What, then, justifies moving from a correct classification to the assumption that we have fully comprehended the thing before us?
2. Nietzsche: How Concepts Are Made
Nietzsche approaches this problem by examining how concepts are formed. In On Truth and Lying in a Non-Moral Sense (1873), he writes: “We obtain the concept, as we do the form, by overlooking what is individual and actual” (Nietzsche, 1999, p. 146). A concept applies to many cases by grouping together things that resemble one another in certain respects while differing in others. The general term leaf becomes possible because distinctions among individual leaves are set aside.
Nietzsche sharpens the point through the imagined original leaf, a model against which actual leaves might appear as imperfect copies. Once differences between individual examples have been disregarded, their shared classification can seem to derive from a common form that exists independently of the act of comparison. An operation performed by us is mistaken for the discovery of an essence already present in nature.
His example of honesty shows how this reversal can shape explanation. We classify several actions as honest and then account for a person's conduct by appealing to “his honesty,” as though the quality named after those actions were their cause. What we inferred from particular actions is subsequently treated as an independent property that explains them.
Nietzsche's criticism concerns the tendency to forget the operation through which a concept is formed and to mistake a useful generalisation for an exhaustive account of what it names. Abstraction remains indispensable to thought, but its usefulness does not establish that the concept captures everything about the things brought under it.
3. The Tree: The Limits of Representation
Nietzsche extends his inquiry from concept formation to perception itself. In §192 of Beyond Good and Evil, he compares reading a page with apprehending a tree. We do not register every word and syllable on a page before understanding its probable sense; similarly, we find it easier to put together an approximation of a tree than to see it in all the detail of its leaves, branches, colours, and shapes (Nietzsche, 2002, §192).
The example shifts the problem from classifying different objects to apprehending an individual one. Even when we attend to a particular tree, perception does not simply deliver every feature it possesses. We select and organise what is available to us, drawing on familiar patterns and expectations to make an impression intelligible. What we see depends partly on what we notice and partly on how we interpret it.
This selectivity does not make perception arbitrary or render the knowledge it provides illusory. We need ways of organising what we perceive, and these can yield genuine knowledge. Nietzsche's example instead invites us to distinguish between apprehending an object and assuming that our apprehension is complete. The same problem that arises when a concept brings different things under one name also arises when we attempt to grasp a single thing through a selective representation.
The question now concerns the conditions under which anything becomes intelligible to us. If our representations are shaped by the ways we apprehend and organise the world, how should we understand the relation between those representations and what they represent?
4. Nietzsche and Kant: What Lies Beyond Our Concepts?
“Nature is acquainted with no forms and no concepts, and likewise with no species, but only with an X which remains inaccessible and undefinable for us.”
— Friedrich Nietzsche, On Truth and Lying in a Non-Moral Sense
The X in Nietzsche's formulation raises a question central to Kant's critical philosophy: what can we know about reality when our knowledge depends on the conditions that make experience possible? In the Critique of Pure Reason, Kant argues that human knowledge depends on the forms of sensibility and the categories of the understanding. We can know objects as they appear under these conditions, but cannot know things in themselves independently of them (Kant, 1781/1998). This distinction marks a limit to theoretical knowledge, since we cannot simply step outside the conditions of experience and describe reality as it exists apart from them.
Nietzsche explicitly invokes the thing in itself in his 1873 essay, bringing his account into direct contact with Kantian terminology. Yet his formulation directs attention to the human operations through which the world becomes intelligible. Nature, he suggests, does not divide itself into the forms, concepts, and species through which we organise experience; what lies beyond these classifications remains an X that we cannot define. Even the distinction between individual and species may be anthropomorphic, although Nietzsche cautions that we cannot establish that it fails to correspond to the essence of things (Nietzsche, 1999, p. 150). His argument thus engages a Kantian problem while developing its own account of how human representations shape our understanding of reality. The X should not simply be equated with Kant's thing in itself, since the two belong to distinct philosophical arguments.
Nietzsche's later retrospective account helps clarify the character of this engagement. In An Attempt at Self-Criticism, added to The Birth of Tragedy in 1886, he acknowledges that his earlier work had employed Kantian and Schopenhauerian formulations to express valuations that ran counter to the spirit of those philosophies (Nietzsche, 1999). This admission shows that his relation to Kant involved both the appropriation of an inherited philosophical vocabulary and a critical reworking of its assumptions. The question of the limits of knowledge becomes, in Nietzsche's essay, an inquiry into how human representations arise and how the conditions through which we understand reality can be mistaken for features of reality itself.
5. Adorno: Non-Identity, Nietzsche, and Hegel
In the introduction to Negative Dialectics, Adorno writes that “the concept does not exhaust the thing conceived” (Adorno, 1973, p. 5). His formulation brings the problem raised by Nietzsche into a different philosophical project. Nietzsche examines how conceptual thought depends on overlooking what is individual and actual: “We obtain the concept, as we do the form, by overlooking what is individual and actual”; Adorno asks what follows when the resulting identification is treated as a sufficient account of its object. Both challenge the assumption that determining what something is amounts to comprehending everything it is.
The connection has a substantial intellectual basis. Adorno acknowledged an exceptional debt to Nietzsche, greater, he said, than his debt to any other major philosopher, including Hegel. The significance of that debt for Negative Dialectics has been explored by Kastrinakis (2025), who argues that Nietzsche's critique of identity and his treatment of truth and error help illuminate the development of Adorno's negative dialectics. This connection helps explain how a problem that Nietzsche explores through the formation and use of concepts becomes, in Adorno, a critique of the claims thought makes to comprehend its objects fully.
Adorno calls the tendency to treat conceptual identification as exhaustive identity thinking. Identifying something means bringing it under a concept, making a determination that can be communicated and examined. The difficulty arises when this determination is treated as complete, so that whatever escapes it appears irrelevant or unintelligible. Non-identity names the failure of the object to coincide fully with its conceptual determination. It does not offer access to the object from a position outside thought; rather, it directs attention to the discrepancy between what a concept enables us to understand and what remains inadequately expressed through it.
Adorno develops this argument through a sustained engagement with Hegel. Hegelian dialectics seeks to comprehend the relation between particular and universal through the movement of the concept, giving contradiction a central role in philosophical thinking. Adorno retains the importance of mediation and contradiction while challenging what he regards as the idealist tendency to bring the movement of thought to completion in a conceptual totality. When the object's otherness is ultimately absorbed into such a unity, the discrepancy between thought and object loses its critical force.
Yet Adorno does not reject reconciliation as a philosophical aim. He writes that “Dialectics serves the end of reconcilement” (Adorno, 1973, p. 18). His objection concerns the claim that reconciliation has already been accomplished within a system that identifies reality with the movement of thought. Reconciliation would release what is different from the compulsion to conform to an established unity; it cannot be achieved merely by declaring a conceptual system complete. Non-identity thus gives Adorno's critique both its object and its direction: thought must examine the inadequacies of its determinations while keeping open the possibility of a less coercive relation between thought and what it seeks to understand.
Nietzsche's critique of conceptual identification helps illuminate Adorno's account of non-identity, while Adorno's engagement with Hegel shows why the problem extends beyond individual acts of classification to the ambitions of philosophy itself.
6. Why the Object Has a History
The implications of Adorno's argument become clearer when we consider how objects acquire significance within social relations. A tree can be understood as a living organism, a source of timber, a habitat, or an element of a landscape. Each description places it within a different set of relations. Forestry brings ownership, labour, production, and exchange into view; an ecological account directs attention to the organisms and environmental conditions sustained by the tree. These contexts shape what matters about the object and how it is understood.
Adorno develops a related argument in “Free Time,” where he examines a phenomenon that appears to be defined by its separation from work. He writes: “Free time is shackled to its opposite. Indeed the oppositional relation in which it stands imbues free time with certain essential characteristics. What is more, and far more importantly, free time depends on the totality of social conditions, which continues to hold people under its spell” (Adorno, 2005, p. 167). His point is that free time cannot be adequately understood in isolation from the social organisation of work. The conditions that supposedly distinguish it from work also shape its character. Its apparent independence therefore conceals a dependence on the wider social relations within which it takes place.
The example brings the historical dimension of Adorno's argument into focus. The categories through which we understand objects and social phenomena are shaped by practices, institutions, and forms of life. When a historically formed category comes to seem natural or self-evident, the conditions under which it emerged can disappear from view, making one way of organising reality appear inevitable. What appears to be an isolated object or an independent sphere of activity may depend on relations that its familiar description leaves unexamined.
For Adorno, the problem is therefore social as well as epistemological. Concepts can conceal the processes through which objects and social relations have acquired their present significance, along with the interests and practices sustained by familiar classifications. Improving our understanding requires examining the relations that give a phenomenon its significance and asking what those relations allow us to see, what they obscure, and how they came to matter.
7. Constellation: Thinking Without Exhausting the Object
How can thought pursue a more adequate understanding of its objects while recognising the limitations of individual concepts? Adorno's answer involves the constellation: a configuration in which concepts are brought into relation around the object they seek to comprehend. In Negative Dialectics, he writes: “By themselves, constellations represent from without what the concept has cut away within” (Adorno, 1973, p. 162). Placing concepts in relation can illuminate aspects of an object that an isolated classification leaves obscure.
The method depends on the work done by the relations among concepts. One concept may identify a feature of an object; another may reveal the conditions under which that feature acquires significance; a third may expose a tension between the object's description and the relations in which it participates. Considered together, these concepts can make their own limitations more visible while developing a more adequate understanding of the object. The aim is not to accumulate definitions until nothing remains to be said, but to let their configuration disclose relations that any single determination leaves out.
Constellation also gives practical form to Adorno's criticism of a completed philosophical system. Inquiry can proceed through mediation and contradiction without treating its present achievements as the definitive measure of reality. A new relation may reveal that a familiar description is inadequate, requiring the constellation to be revised. The object remains open to further determination because understanding depends on relations that no single configuration can guarantee it has exhausted.
Return, finally, to the leaf. The concept leaf enables us to recognise it; concepts drawn from botany, ecology, or the history of a particular landscape can disclose other aspects of its structure and significance. Considered together, these perspectives deepen our understanding by showing how features of the leaf belong to wider relations. They do not provide a view from nowhere or a final account of the object. They make our understanding more adequate by allowing what each concept leaves out to become visible through the others.
The task of thought is to make its concepts answerable to what they seek to comprehend. Nietzsche exposes the operation through which conceptual identities are formed and examines the selectivity of representation. Kant establishes a critical problem concerning the conditions and limits of human knowledge, which Nietzsche explicitly engages and reworks. Adorno develops a critique of conceptual identification informed by his substantial debt to Nietzsche and his sustained engagement with Hegel. Constellation expresses the method that follows from this critique: understanding an object through the relations among concepts, while keeping open the possibility that the object may require us to think differently.
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; second edition published 1787)
Kastrinakis, N. (2025). Adorno’s negative dialectics and its debt to Nietzsche: Could Nietzsche be the originator of Adorno’s negative dialectics? Philosophy & Social Criticism, 51(9), 1436–1468.
Nietzsche, F. (1999). The birth of tragedy and other writings (R. Geuss & R. Speirs, Eds.; R. Speirs, Trans.). Cambridge University Press.
Nietzsche, F. (2002). Beyond good and evil: Prelude to a philosophy of the future (J. Norman, Trans.; R.-P. Horstmann, Ed.). Cambridge University Press. (Original work published 1886)
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