A concept is a sum of thought, which, when linked to other sum of thought, can form a proposition. A concept is a signifier which can be expressed by means of a signifier (a word or a statement), and it has an abstract character, for example the content of “man” or “white” (examples of Aristotle). A concept differs from the thing designated by this concept. The term concept is thematized in the Middle Ages (conceptus), by Thomas Aquinas then Guillaume d’Ockham and the other scholastic philosophers. The term concept comes from the Latin conceptus which means “contain, hold together”, derived from the verb concipere meaning “to conceive”.
Modern philosophers (Descartes, Locke) will substitute for the concept the notion of idea, which more generally refers to any mental representation, whether perceptual, imaginary or purely abstract.
Different philosophers do not necessarily agree on exactly what is a concept, beyond these general definitions, although central lines can be drawn. Thus, a concept is often a general idea (the dog concept gathers all existing and possible dogs), but not necessarily: for Leibniz, the complete notion expresses the individual substance and corresponds only to it.
The coin of the notion of concept in antiquity
The concept has been very often assimilated to the meaning of a term, in the sense of intension, or denotation of that term. Thus, the concepts of objects would be the set of predicates which belong to it, or which are, in Aristotelian language, predicated of a subject. Perhaps Aristotle believes that a good concept is a concept that refers to the essence, not the proper one: thus the concept of man is not “the animal capable of laughing” (laughter is the characteristic of man: only man laughs, not his essence), but a “reasonable animal” or a “political animal” (zoon politikon). In other words, the concept should express the quiddity of the thing.
The elaboration of concept of concept in scholasticism
Assimilated to the intension of a term, the concept was thus considered by medieval philosophy as a mental representation, which refers to a series of objects. The quarrel of universals opposed the nominalists (or “terminists”) to the realists, about the ontological status of universals, which are concepts like “man” or “animal.”
Nominalism considers that concepts have no real or extra-mental existence, they are only psychological and subjective. The nominalists think that only concrete individuals actually exist.
William of Ockham, in the thirteenth century, is one of the principal representatives of nominalism. Claude Panaccio, a medievalist and a specialist in his thought, summed it up: “William d’Ockham […] proposed to see concepts as signs whose function would be to represent in the mind not abstract objects of special nature or universals such as man or animal in general, but concrete singular things”.
This position influenced later philosophers such as George Berkeley, who thinks that words only serve to designate collections of perceptions rather than abstract ideas, or Nelson Goodman, who explicitly claims the nominalist position in Steps Toward a Constructive Nominalism in 1947.
Realism, on the contrary, considers that the universals (“man”, for example) have a real and extra-mental existence, which guarantees their objectivity and their public (as opposed to private, subjective) character. Platonism is also referred to, since Plato admitted the existence of forms or intelligible ideas independent of the subjective mental acts which aim at them. This position will be taken up by Gottlob Frege, who is at the origin of contemporary logic and analytic philosophy. To describe this ontological position, Claude Panaccio speaks of “Platonism of concepts.”
The conceptualism of Pierre Abelard constitutes a middle way between nominalism and realism. It will later be claimed by the American philosopher Willard Van Orman Quine in his book From the Logical Point of View in 1953.
The three positions can be summarized thus: for the realism, the universals exist ante rem (before the singular things), for the nominalism exist post rem (after the things, they are drawn) and for the conceptualism they exist in re (in things). The philosopher and theologian Thomas Aquinas, however, affirms the three propositions together: “According to St. Thomas, universals exist at the same time ante rem, that is to say, in the divine understanding before Creation, in re: in Created things that update them, and post rem: in the human mind that conceives them”.
Modern philosophy: from concept to idea
Modern philosophers call the concept an “idea” or representation of the mind, singular (perceptive), or which abbreviates and summarizes a multiplicity of empirical or mental objects by abstraction and generalization of identifiable common traits.
The concept is, according to Kant, what unifies the diverse of sensation. Kant defines the supreme concepts of knowledge as categories of the understanding, in the Critique of Pure Reason.
In linguistics, it will be said that the concept is denoted in language by a term which designates it: the concept is called signified, the term designating it is called signifier.
Empiricism, rationalism and idealism, each one propose their definition of the concept and theorize its genesis and its role in knowledge.
Translation from Wikipedia