Conceptualism holds that universals exist, but not as mind-independent entities in the world or as mere names applied arbitrarily to things. Instead, conceptualists argue that universals exist as concepts or mental representations formed by the mind in response to genuine patterns or similarities encountered in experience. On this view, redness, triangularity, or justice are real, but their reality is grounded in the cognitive operations of minds that perceive and abstract common features from particulars. Conceptualism occupies the middle ground in the Universals - Debate between realism, which locates universals in the world independently of minds, and nominalism, which denies that universals are anything more than words or names.
Conceptualism is held by philosophers working across rationalist, empiricist, and Kantian traditions, and has attracted adherents from medieval Scholasticism through contemporary philosophy of mind and language.
Universals are mental abstractions, not Platonic forms. Conceptualists argue that when a mind encounters multiple red objects, it performs an act of abstraction, forming a concept that captures what those objects share. The universal “redness” is this concept - a mental representation that can be applied across instances. It has genuine cognitive content and is not merely a sound or a label, but it does not float free of minds in a Platonic realm.
Genuine similarity grounds concept formation. Unlike strict nominalists, conceptualists typically hold that the world provides genuine grounds for the concepts we form. Objects are not similar merely because we happen to call them by the same name; rather, minds form common concepts because things in the world really do resemble each other in relevant respects. The concept tracks something in reality, even if the universal itself is a mental entity rather than a worldly one.
Universals require minds, but are not arbitrary. Conceptualists contend that universals depend on the existence of minds for their being, but this does not make them subjective in the sense of being random or conventional. The concept of triangularity applies to all triangles because those figures share genuine geometrical properties that the mind reliably recognizes. The mind-dependence of universals does not collapse into relativism.
Abstraction explains predication. When we say “this apple is red,” conceptualists argue that we predicate a concept - the universal red - of a particular. The concept is multiply applicable because the mind has abstracted it from many instances and recognizes it as applying wherever the relevant similarity obtains. This account is held to explain how general terms function without requiring either abstract objects or a purely deflationary treatment of predication.
The ontological economy argument. Some conceptualists invoke parsimony: positing abstract Platonic universals requires a substantial metaphysical commitment to entities that are causally inert and epistemically puzzling. Conceptualism is held to preserve what is genuinely explanatory about universals - their role in grounding thought, predication, and classification - while avoiding the ontological extravagance of realism.
The conceptualist position was articulated in medieval philosophy primarily in the context of the problem of universals as framed through the reception of Porphyry's Isagoge. Peter Abelard (1079-1142) is often credited with the earliest sustained defense of a recognizably conceptualist view. Abelard rejected both the extreme realism of William of Champeaux, who held that a single universal substance is wholly present in each particular, and the nominalism attributed to Roscellinus, who reportedly reduced universals to mere vocal sounds (voces). For Abelard, the universal is a sermo - a meaningful word - whose meaning consists in a concept formed by the intellect abstracting from particulars. The universal exists in the mind but is genuinely informative about the world because the resemblances it tracks are real.1)
In the early modern period, John Locke gave an empiricist articulation of conceptualism in An Essay Concerning Human Understanding (1689). Locke argued that general terms signify abstract general ideas formed by the mind through a process of selective attention: the mind notices common features across particular experiences and assembles them into a general concept. This concept - the abstract idea - is the meaning of the general term and constitutes the universal. Locke's account was subjected to influential criticism by George Berkeley, who argued that there are no coherent abstract ideas of the kind Locke described, and by David Hume, who replaced abstract ideas with a theory of resemblance classes. These challenges pushed later conceptualists to refine the account of how concepts represent without requiring a perfectly determinate mental image.2)
Immanuel Kant's critical philosophy gave conceptualism a new form. For Kant, pure concepts of the understanding (categories) are not derived from experience through abstraction but are the conditions that make experience possible. While this applies primarily to structural concepts like causality and substance rather than to empirical universals like redness, Kant's framework encouraged a broadly conceptualist orientation in which the activity of the mind is constitutive of the general structure of experience. Neo-Kantian and idealist traditions in the nineteenth century developed these themes further.
In the twentieth century, conceptualism was revisited in connection with philosophy of language and philosophy of mind. Wilfrid Sellars, though resistant to simple labels, developed accounts of concept use and predication that share affinities with conceptualism. More recently, debates about concepts in cognitive science have given the position new empirical grounding, as researchers investigate how the mind forms, stores, and applies category representations.
Peter Abelard (1079-1142) - Medieval philosopher and theologian whose Logica Ingredientibus and Logica Nostrorum Petitioni Sociorum contain the most detailed surviving early defense of a conceptualist-adjacent position, arguing that universals are meaningful terms (sermones) whose significance consists in shared mental content grounded in real resemblances.
John Locke (1632-1704) - Empiricist philosopher whose theory of abstract general ideas in the Essay Concerning Human Understanding represents the canonical early-modern statement of conceptualism. Locke held that the mind forms abstract ideas by separating the common features of experienced particulars, and that these ideas are what general words signify.
Immanuel Kant (1724-1804) - Although Kant's position is complex and not reducible to classical conceptualism, his insistence that concepts are products of the spontaneous activity of the understanding, rather than mind-independent forms grasped by the intellect, has been deeply influential on conceptualist thinking.
Wilfrid Sellars (1912-1989) - American philosopher whose work on predication, abstract entities, and the role of linguistic and conceptual frameworks in structuring experience led some interpreters to classify him as a sophisticated conceptualist. His paper “Abstract Entities”3) engages directly with questions central to the universals debate.
Colin McGinn (b. 1950) - Among contemporary philosophers, McGinn has defended positions in which concepts as mental particulars play the role universals are classically assigned, holding that concept possession rather than relation to abstract objects explains our general thought and talk.
Whether concepts are mental particulars or mental types. A recurring tension concerns the status of concepts themselves. If a concept is a mental particular - a token in a given mind - then two people thinking about redness have numerically distinct concepts, and it is unclear what makes them the same concept. Some conceptualists resolve this by appealing to a resemblance relation among concepts, but this risks regress. Others invoke mental types, though this move is sometimes seen as reintroducing a form of realism at the level of concept-types.
The source of concepts: abstraction versus innate endowment. Empiricist conceptualists hold that concepts are formed through abstraction from experience, while rationalist and Kantian conceptualists hold that at least some concepts are innate or a priori structures of the mind. This division affects how conceptualists respond to nominalist critiques and how they account for concepts of mathematical or necessary truths.
Whether conceptualism can handle mathematical universals. Critics from both the realist and nominalist sides press conceptualists on the case of mathematics. Mathematical truths appear necessary and mind-independent; conceptualists must explain how mental concepts can yield such truths. Some conceptualists argue that mathematical concepts are constructed by the mind but generate necessary truths because of how those constructions work; others concede that mathematical universals may require a more realist treatment, producing hybrid positions.
The publicity of concepts and shared understanding. If universals are concepts in individual minds, it is disputed how communication and shared understanding are possible. Two people using the word “red” must in some sense share the concept. Conceptualists variously appeal to the uniformity of human cognitive faculties, the causal role of shared experiences, or the normativity of concept use to bridge this gap.
1. John Marenbon, The Philosophy of Peter Abelard (Cambridge: Cambridge University Press, 1997), 174-197. 2. John Locke, An Essay Concerning Human Understanding, ed. Peter H. Nidditch (Oxford: Clarendon Press, 1975), III.iii.6-9. 3. Wilfrid Sellars, “Abstract Entities,” Review of Metaphysics 16, no. 4 (1963): 627-671.