Editing Concept (section)

== Notable theories on the structure of concepts ==

=== Classical theory ===
{{Main article|Definitionism}}

The classical theory of concepts, also referred to as the empiricist theory of concepts,<ref name="Origin of Concepts"/> is the oldest theory about the structure of concepts (it can be traced back to Aristotle<ref name="Big Book"/>), and was prominently held until the 1970s.<ref name="Big Book"/> The classical theory of concepts says that concepts have a definitional structure.<ref name="Stanford Encycl"/> Adequate definitions of the kind required by this theory usually take the form of a list of features. These features must have two important qualities to provide a comprehensive definition.<ref name="Big Book"/> Features entailed by the definition of a concept must be both ''[[necessity and sufficiency|necessary]]'' and jointly ''[[necessity and sufficiency|sufficient]]'' for membership in the class of things covered by a particular concept.<ref name="Big Book" /> A feature is considered necessary if every member of the denoted class has that feature. A set of features is considered sufficient if having all the parts required by the definition entails membership in the class.<ref name="Big Book" /> For example, the classic example ''[[bachelor]]'' is said to be defined by ''unmarried'' and ''[[man]]''.<ref name="Stanford Encycl"/> An entity is a bachelor (by this definition) if and only if it is both unmarried and a man. To check whether something is a member of the class, you compare its qualities to the features in the definition.<ref name="Origin of Concepts"/> Another key part of this theory is that it obeys the ''[[law of the excluded middle]]'', which means that there are no partial members of a class, you are either in or out.<ref name="Big Book"/>

The classical theory persisted for so long unquestioned because it seemed intuitively correct and has great explanatory power. It can explain how concepts would be acquired, how we use them to categorize and how we use the structure of a concept to determine its referent class.<ref name="Stanford Encycl"/> In fact, for many years it was one of the major activities in [[philosophy]]—[[formal concept analysis|concept analysis]].<ref name="Stanford Encycl"/> Concept analysis is the act of trying to articulate the necessary and sufficient conditions for the membership in the referent class of a concept.{{citation needed|date=December 2012}} For example, Shoemaker's classic "[[Time Without Change]]" explored whether the concept of the flow of time can include flows where no changes take place, though change is usually taken as a definition of time.{{citation needed|date=August 2020}}

==== Arguments against the classical theory ====
Given that most later theories of concepts were born out of the rejection of some or all of the classical theory,<ref name="concepts core readings"/> it seems appropriate to give an account of what might be wrong with this theory. In the 20th century, philosophers such as Wittgenstein and Rosch argued against the classical theory. There are six primary arguments<ref name="concepts core readings"/> summarized as follows:
* It seems that there simply are no definitions—especially those based in sensory primitive concepts.<ref name="concepts core readings"/>
* It seems as though there can be cases where our ignorance or error about a class means that we either don't know the definition of a concept, or have incorrect notions about what a definition of a particular concept might entail.<ref name="concepts core readings"/>
* [[Willard Van Orman Quine|Quine]]'s argument against analyticity in [[Two Dogmas of Empiricism]] also holds as an argument against definitions.<ref name="concepts core readings"/>
* Some concepts have fuzzy membership. There are items for which it is vague whether or not they fall into (or out of) a particular referent class. This is not possible in the classical theory as everything has equal and full membership.<ref name="concepts core readings"/>
* Experiments and research showed that assumptions of well defined concepts and categories might not be correct. Researcher Hampton<ref>{{cite journal |last1=Hampton |first1=J.A. |title=Polymorphous concepts in semantic memory. |journal=Journal of Verbal Learning and Verbal Behavior |date=1979 |volume=18 |issue=4 |pages=441–461|doi=10.1016/S0022-5371(79)90246-9 }}</ref> asked participants to differentiate whether items were in different categories. Hampton did not conclude that items were either clear and absolute members or non-members. Instead, Hampton found that some items were barely considered category members and others that were barely non-members. For example, participants considered sinks as barely members of kitchen utensil category, while sponges were considered barely non-members, with much disagreement among participants of the study. If concepts and categories were very well defined, such cases should be rare. Since then, many researches have discovered borderline members that are not clearly in or out of a category of concept.
* [[Eleanor Rosch|Rosch]] found typicality effects which cannot be explained by the classical theory of concepts, these sparked the prototype theory.<ref name="concepts core readings"/> See below.
* Psychological experiments show no evidence for our using concepts as strict definitions.<ref name="concepts core readings"/>

=== Prototype theory ===
{{Main article|Prototype theory}}

Prototype theory came out of problems with the classical view of conceptual structure.<ref name="Stanford Encycl"/> Prototype theory says that concepts specify properties that members of a class tend to possess, rather than must possess.<ref name="concepts core readings"/> [[Ludwig Wittgenstein|Wittgenstein]], [[Eleanor Rosch|Rosch]], Mervis, [[Brent Berlin]], Anglin, and [[Michael Posner (psychologist)|Posner]] are a few of the key proponents and creators of this theory.<ref name="concepts core readings"/><ref name="new paradigm">{{cite book|last=Brown|first=Roger|title=A New Paradigm of Reference|year=1978|publisher=Academic Press Inc|isbn=978-0-12-497750-1|pages=159–166}}</ref> Wittgenstein describes the relationship between members of a class as ''family resemblances''. There are not necessarily any necessary conditions for membership; a dog can still be a dog with only three legs.<ref name="Big Book"/> This view is particularly supported by psychological experimental evidence for prototypicality effects.<ref name="Big Book"/> Participants willingly and consistently rate objects in categories like 'vegetable' or 'furniture' as more or less typical of that class.<ref name="Big Book"/><ref name="new paradigm"/> It seems that our categories are fuzzy psychologically, and so this structure has explanatory power.<ref name="Big Book"/> We can judge an item's membership of the referent class of a concept by comparing it to the typical member—the most central member of the concept. If it is similar enough in the relevant ways, it will be cognitively admitted as a member of the relevant class of entities.<ref name="Big Book"/> Rosch suggests that every category is represented by a central exemplar which embodies all or the maximum possible number of features of a given category.<ref name="Big Book"/> Lech, Gunturkun, and Suchan explain that categorization involves many areas of the brain. Some of these are: visual association areas, prefrontal cortex, basal ganglia, and temporal lobe.

The Prototype perspective is proposed as an alternative view to the Classical approach. While the Classical theory requires an all-or-nothing membership in a group, prototypes allow for more fuzzy boundaries and are characterized by attributes.<ref name="prototype in linguistic theory">{{Cite book|url=https://philpapers.org/rec/TAYLCP-3|title=Linguistic Categorization: Prototypes In Linguistic Theory|last=TAYLOR|first=John R.|date=1989}}</ref> Lakoff stresses that experience and cognition are critical to the function of language, and Labov's experiment found that the function that an artifact contributed to what people categorized it as.<ref name="prototype in linguistic theory"/> For example, a container holding mashed potatoes versus tea swayed people toward classifying them as a bowl and a cup, respectively. This experiment also illuminated the optimal dimensions of what the prototype for "cup" is.<ref name="prototype in linguistic theory"/>

Prototypes also deal with the essence of things and to what extent they belong to a category. There have been a number of experiments dealing with questionnaires asking participants to rate something according to the extent to which it belongs to a category.<ref name="prototype in linguistic theory"/> This question is contradictory to the Classical Theory because something is either a member of a category or is not.<ref name="prototype in linguistic theory"/> This type of problem is paralleled in other areas of linguistics such as phonology, with an illogical question such as "is /i/ or /o/ a better vowel?" The Classical approach and Aristotelian categories may be a better descriptor in some cases.<ref name="prototype in linguistic theory"/>

=== Theory-theory ===
{{Main|Theory-theory}}
Theory-theory is a reaction to the previous two theories and develops them further.<ref name="Big Book"/> This theory postulates that categorization by concepts is something like scientific theorizing.<ref name="Stanford Encycl"/> Concepts are not learned in isolation, but rather are learned as a part of our experiences with the world around us.<ref name="Big Book"/> In this sense, concepts' structure relies on their relationships to other concepts as mandated by a particular mental theory about the state of the world.<ref name="concepts core readings"/> How this is supposed to work is a little less clear than in the previous two theories, but is still a prominent and notable theory.<ref name="concepts core readings"/> This is supposed to explain some of the issues of ignorance and error that come up in prototype and classical theories as concepts that are structured around each other seem to account for errors such as whale as a fish (this misconception came from an incorrect theory about what a whale is like, combining with our theory of what a fish is).<ref name="concepts core readings"/> When we learn that a whale is not a fish, we are recognizing that whales don't in fact fit the theory we had about what makes something a fish. Theory-theory also postulates that people's theories about the world are what inform their conceptual knowledge of the world. Therefore, analysing people's theories can offer insights into their concepts. In this sense, "theory" means an individual's mental explanation rather than scientific fact. This theory criticizes classical and prototype theory as relying too much on similarities and using them as a sufficient constraint. It suggests that theories or mental understandings contribute more to what has membership to a group rather than weighted similarities, and a cohesive category is formed more by what makes sense to the perceiver. Weights assigned to features have shown to fluctuate and vary depending on context and experimental task demonstrated by Tversky. For this reason, similarities between members may be collateral rather than causal.<ref>{{Cite journal|last1=Murphy|first1=Gregory L.|last2=Medin|first2=Douglas L.|date=1985|title=The role of theories in conceptual coherence.|journal=Psychological Review|volume=92|issue=3|pages=289–316|doi=10.1037/0033-295x.92.3.289|pmid=4023146|issn=0033-295X}}</ref>