[Paleopsych] Concepts from the Routledge Encyclopedia of Philosophy

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Subject: Concepts from the Routledge Encyclopedia of Philosophy

Concepts from the Routledge Encyclopedia of Philosophy

The topic of concepts lies at the intersection of semantics and philosophy of 
mind. A concept is supposed to be a constituent of a thought (or 'proposition') 
rather in the way that a word is a constituent of a sentence that typically 
expresses a thought. Indeed, concepts are often thought to be the meanings of 
words (and will be designated by enclosing the words for them in brackets: 
[city] is expressed by 'city' and by 'metropolis'). However, the two topics can 
diverge: non-linguistic animals may possess concepts, and standard linguistic 
meanings involve conventions in ways that concepts do not.

Concepts seem essential to ordinary and scientific psychological explanation, 
which would be undermined were it not possible for the same concept to occur in 
different thought episodes: someone could not even recall something unless the 
concepts they have now overlap the concepts they had earlier. If a disagreement 
between people is to be more than 'merely verbal', their words must express the 
same concepts. And if psychologists are to describe shared patterns of thought 
across people, they need to advert to shared concepts.

Concepts also seem essential to categorizing the world, for example, 
recognizing a cow and classifying it as a mammal. Concepts are also 
compositional: concepts can be combined to form a virtual infinitude of complex 
categories, in such a way that someone can understand a novel combination, for 
example, [smallest sub-atomic particle], by understanding its constituents.

Concepts, however, are not always studied as part of psychology. Some logicians 
and formal semanticists study the deductive relations among concepts and 
propositions in abstraction from any mind. Philosophers doing 'philosophical 
analysis' try to specify the conditions that make something the kind of thing 
it is - for example, what it is that makes an act good - an enterprise they 
take to consist in the analysis of concepts.

Given these diverse interests, there is considerable disagreement about what 
exactly a concept is. Psychologists tend to use 'concept' for internal 
representations, for example, images, stereotypes, words that may be the 
vehicles for thought in the mind or brain. Logicians and formal semanticists 
tend to use it for sets of real and possible objects, and functions defined 
over them; and philosophers of mind have variously proposed properties, 
'senses', inferential rules or discrimination abilities.

A related issue is what it is for someone to possess a concept. The 'classical 
view' presumed concepts had 'definitions' known by competent users. For 
example, grasping [bachelor] seemed to consist in grasping the definition, 
[adult, unmarried male]. However, if definitions are not to go on forever, 
there must be primitive concepts that are not defined but are grasped in some 
other way. Empiricism claimed that these definitions were provided by sensory 
conditions for a concept's application. Thus, [material object] was defined in 
terms of certain possibilities of sensation.

The classical view suffers from the fact that few successful definitions have 
ever been provided. Wittgenstein suggested that concept possession need not 
consist in knowing a definition, but in appreciating the role of a concept in 
thought and practice. Moreover, he claimed, a concept need not apply to things 
by virtue of some closed set of features captured by a definition, but rather 
by virtue of 'family resemblances' among the things, a suggestion that has 
given rise in psychology to 'prototype' theories of concepts.

Most traditional approaches to possession conditions have been concerned with 
the internal states, especially the beliefs, of the conceptualizer. Quine 
raised a challenge for such an approach in his doctrine of confirmation 
holism', which stressed that a person's beliefs are fixed by what they find 
plausible overall. Separating out any particular beliefs as defining a concept 
seemed to him arbitrary and in conflict with actual practice, where concepts 
seem shared by people with different beliefs. This led Quine himself to be 
sceptical about talk of concepts generally, denying that there was any 
principled way to distinguish 'analytic' claims that express definitional 
claims about a concept from 'synthetic' ones that express merely common beliefs 
about the things to which a concept applies.

However, recent philosophers suggest that people share concepts not by virtue 
of any internal facts, but by virtue of facts about their external (social) 
environment. For example, people arguably have the concept [water] by virtue of 
interacting in certain ways with H2O and deferring to experts in defining it. 
This work has given rise to a variety of externalist theories of concepts and 
semantics generally.

Many also think, however, that psychology could generalize about people's minds 
independently of the external contexts they happen to inhabit, and so have 
proposed 'two-factor theories', according to which there is an internal 
component to a concept that may play a role in psychological explanation, as 
opposed to an external component that determines the application of the concept 
to the world.

   1. Concepts as shareable constituents of thought
   2. Meanings of words
   3. Concepts and analysis
   4. Referential views
   5. Possession conditions: external v. internal
   6. The classical view and empiricism
   7. Inferential roles and prototypes
   8. Metaphysics v. epistemology
   9. Difficulties for an internalist approach
   10. Two-factor theories and a modified classical view

1. Concepts as shareable constituents of thought

Constituents of thought. It is widely thought that 'intentional' explanation in 
terms of such states as belief, thought and desire affords the best explanation 
of the behaviour and states of people, many animals and perhaps some machines: 
someone drinks water because they have a thirst which they think water will 
quench. By and large, philosophers and psychologists such as Fodor (1975, 1991) 
or Peacocke (1992) who are interested in intentional explanation take 
themselves to be committed to the existence of concepts, whereas those 
sceptical of this form of explanation, for example, Quine (1960), tend to avoid 
them (see Animal language and thought; Cognitive development; Intentionality).

Suppose one person thinks that water dissolves salt, and another that it does 
not. Call the thing that they disagree about a 'proposition' - for example, 
[Water dissolves salt]. It is in some sense shared by them as the object of 
their disagreement, and it is expressed by the sentence that follows the verb 
'thinks that'. Concepts are the constituents of such propositions (in at least 
one understanding of them; see Propositions, sentences and statements), just as 
the words 'water', 'dissolves' and 'salt' are constituents of the sentence. 
Thus, these people could have these beliefs only if they had, inter alia, the 
concepts [water], [dissolves], [salt].

Just which sentential constituents express concepts is a matter of some debate. 
The central cases that are discussed tend to be the concepts expressed by 
predicates or general terms, such as is water' or 'x dissolves y', terms 
potentially true of many different individual things. But there are presumably 
concepts associated with logical words (for example, [not], [some]), as well as 
with individual things (for example, [Rome], [2]).

Shareability. If we are to make sense of processes of reasoning and 
communication, and have a basis for generalization in a cognitive psychology, 
then concepts must be shareable. Consequently, concepts need to be 
distinguished from the particular ideas, images, sensations that, consciously 
or unconsciously, pass through people's minds at a particular time. The concept 
[cat] could not be some individual experience someone has, since in that case 
no two people could share it and a single person probably could not have the 
same one twice. Just what kind of shareable object a concept might be is a 
matter of considerable disagreement among theorists. In much of the 
psychological literature, where the concern is often with features of actual 
mental processing, concepts are regarded as mental representations, on such as 
words or images.

It will be important with respect to this and later proposals to invoke a 
distinction from the study of language between types and tokens (see Type/token 
distinction). A linguistic token, such as an inscription of 'café' on a door, 
has a specific spacetime location: one can ask when and where it occurs; 
whereas a linguistic type - the word 'café' - like any 'universal', is an 
abstract object outside space and time. One can erase a token of the word 
'café', but the type word would still exist. Similarly, concepts could be 
regarded as internal representation types that have individual ideas as their 
specific tokens. On this view, you and I could share the concept [water] if you 
and I have tokens of the same representation type in our minds or brains. There 
is a good deal of discussion in psychology as to whether concepts in this sense 
are (type) words, phrases, pictures, maps, diagrams or other kinds of 
representations, for example, prototypes or 'exemplars' (see §7 below; and 
Smith and Medin (1981); Rips (1995) for reviews of the psychological 

But many philosophers take the view that these mental representation types 
would no more be identical to concepts than are the type words in a natural 
language. Words in a language are usually individuated syntactically, allowing 
both spoken and written tokens of a word to be of the same type, and 
syntactically identical tokens (for example, of 'bank') to be ambiguous, or of 
different semantic types. Moreover, different syntactic types - for example, 
'city', 'metropolis' - can be synonymous, that is, be of the same semantic 
type. Similarly, one person might express the concept [city] by a mental 
representation 'city', another by 'metropolis'; still another perhaps by a 
mental image of bustling boulevards. But, for all that, they might have the 
same concept [city]: one could believe and another doubt that cities are 
healthy places to live. Moreover, different people could employ the same 
representation to express different concepts: one person might use an image of 
bustling boulevards to express [city], another to express [pollution]. So, on 
the standard philosophical reading (which we shall follow here), concepts are 
to be individuated differently from the representations that express them.

However, although concepts understood in this latter way are arguably also 
indispensable to psychology, they raise different issues from those concerning 
representations that standardly interest psychologists. Questions about 
representations typically involve just the issues that psychologists have 
tended to investigate: processing time, ease of judgment, susceptibility to 
errors. If one person represents cities and their relations 'spatially', where 
another represents them by names and descriptions, this may explain differences 
in how rapidly the two of them can answer questions about cities; but, again, 
presumably they both still have the concept [city]. Just why they would, what 
the possession conditions for [city] or any concept might be, is not easy to 
say (see §5): the point here is that they seem to involve issues different from 
the issue of identifying a syntactically defined representation.

This difference between the psychologist's and philosopher's typical interest 
is sometimes obscured by ambiguous phrasing. When Kant identifies 'analytic' 
claims (or claims that express the 'analysis' of a concept) as those in which 
one concept is contained in' another, he glosses this by saying: 'I have merely 
to analyse the concept, that is, to become conscious to myself of the manifold 
which I always think in that concept' (1781/1787: A7). In our terms, this could 
be read as a claim about representations, or (presumably what he intended) 
about the concepts they express. My mental representation of freedom might 
invariably involve an image of dancing people, but surely neither Kant nor I 
would want to say that the analysis of my concept of freedom involved dancing. 
Conversely, there is no reason that a good analysis should serve as a 
representation in ordinary, rapid reasonings (for example, identifying 
something as a bird): indeed, vivid images might serve better.

2. Meanings of words

As most of our examples suggest, concepts are presumed to serve as the meanings 
of linguistic items, underwriting relations of translation, definition, 
synonymy, antinomy and semantic implication (Katz 1972). Indeed, much work in 
the semantics of natural languages (see Jackendoff 1987) takes itself to be 
addressing 'conceptual structure'. This is partly motivated by Grice's (1957) 
proposal to understand linguistic meaning ultimately in terms of the intentions 
with which speakers produce linguistic tokens: 'good' means what it does at 
least partly because of what users of the word have intended to mean by it; 
that is, because of the concept they have intended to express (see Meaning and 
communication; Grice, H.P. §2).

One problem with this role for concepts is that it is by no means clear just 
what a theory of meaning is supposed to involve. Some of the issues are exactly 
the issues we are considering here. However, some issues seem peculiar to 
language: for example, how much of what is understood in the uttering of a 
sentence is part of its meaning, or semantics, and how much is part of its use, 
and so an issue of pragmatics? (See Pragmatics.) If I say of someone 'He is not 
very good at chess', is the meaning simply that 'It is not the case that he is 
very good', or 'He is bad at chess'?

3. Concepts and analysis

Objects of analysis. At least since Plato's Euthyphro, philosophers have been 
fascinated by a certain sort of question about constitutiveness: in virtue of 
what is something the kind of thing it is - for example, what is 'essential' to 
something's being good, a piece of knowledge, a free act? Obviously, not just 
any truth about the target phenomenon will suffice as an answer: to take 
Plato's Euthyphro example, merely the fact that the gods love the good is no 
reason to think that that is what makes something good, any more than that all 
bachelors eat is what makes them bachelors (see Conceptual analysis).

Some philosophers think such questions are answered by natural science. This 
certainly seems to be true in the case of 'natural kinds' such as water or 
polio, which arguably have 'real essences' largely independently of us (see 
Kripke [1972] 1980; Putnam 1975; Essentialism). But many concepts, such as 
[magic], [freedom], [soul] may not pick out any real kind of thing at all (much 
less one studiable by science): in these cases, all that seems shareable by 
different possessors of the concept is some belief or other. But even in the 
natural science cases, some conceptual analysis seems to many unavoidable, if 
only to determine exactly what the science is about (what makes an 
investigation one about water, or polio, or consciousness; Bealer 1987).

There is a related question that concepts are also sometimes recruited to 
answer; not a metaphysical question about 'the nature of things', but an 
epistemological one about how people seem to know a priori (or 'independently 
of experience') various necessary truths, for example, that there is an 
infinity of prime numbers or that equiangular triangles are equilateral ones. 
However, it should be seen as a substantive and controversial hypothesis, to 
which we will return, whether this epistemological interest should coincide 
with the above metaphysical one (see A priori; §5 below).

Philosophers have also sometimes hoped that conceptual analysis would help 
(dis)solve certain philosophical questions about, for example, truth, free 
will, personal identity, either by clarifying the commitments of the relevant 
concepts, or by showing that they were somehow defective. A once popular 
strategy was to show that the application of a concept was not 'verifiable' (§5 
below). A more recent strategy is to show that the application of a purported 
concept would be unintelligible, as in the case of [absolute space] (Peacocke 
1992: ch. 8).

Whatever its ultimate philosophical benefits, conceptual analysis does seem to 
involve the sort of facts that are relevant to the question of concept 
possession. Returning to our pair of people who represent cites differently: 
what seems relevant to the question of whether, despite their different 
representations, they still have the same concept [city] is what sorts of 
things they believe are essential to being a city; what things they would and 
would not count as cities (which is not to say that this would be decisive; see 
§5). This difference can lend an air of unreality to philosophical as opposed 
to psychological discussions of concepts, depending, as it does, upon difficult 
questions about what (one would think) is possible in various often very 
outlandish situations.

Vagueness. One supposed defect of many concepts should be set aside from the 
start. The belief in constitutive analyses of a concept is often thought to be 
undermined by the existence of difficult, borderline cases for its application 
(Wittgenstein 1953: §§66-7; Smith and Medin 1981: 31). Now, it certainly cannot 
be denied that the world is full of genuine borderline cases: 'Is drizzle 
rain?', 'Are viruses alive?'. Arguably, the world does not supply determinate 
answers: all kinds in the world may have vague boundaries, any precise 
delimitation of which may depend upon human decision. But this does not imply 
that all applications of concepts are up to human decision, much less that 
there are no defining essences of the phenomena they pick out. [Unmarried adult 
male] may be a perfectly good analysis of [bachelor] not only despite hard 
cases, but because the hard cases for the one correspond exactly to the hard 
cases for the other. (See Vagueness.)

4. Referential views

One candidate for the common object of people's thoughts has been simply the 
referents of their representations, that is, the objects in the world picked 
out by them. Someone might say that two representations express the same 
concept if and only if they refer to the same thing(s) in the world. Putting 
aside the difficult problem of explaining 'reference', this seems an appealing 
suggestion, clearest in the case of (token) proper names such as 'Aristotle' 
where the name refers to a specific person (see proper names). When we turn to 
predicates, however, things are not so clear. There are a number of different 
candidates for what counts as the 'referent' of a predicate and so of the 
concept it would express: (1) its extension, (2) its intension (as function), 
and (3) the property that all the (possible) objects satisfying it have in 

Extensions. The 'extension' is the set of actual objects that satisfy the 
concept. For example, the extension of [city] might be the set of cities: 
{Paris, London, Madrid,h}. Russell (1956) proposed an account of 'propositions' 
according to which they were composed of real objects in the world combined 
with properties (see also Kaplan 1979). Extensional logicians such as Goodman 
(1951) and Quine (1960) think that sets of actual objects are all that are 
needed for serious science: all that needs to be mentioned are actual lions, 
tigers and quarks. They realize that this suggestion clashes with our ordinary 
understanding. [Cordate] is not the same as [renate], despite the fact that 
(let us suppose) all and only actual creatures with kidneys are creatures with 
hearts ([renate] and [cordate] are 'coextensive'). It seems reasonable to 
require concepts to cover possible cases, for example, possible creatures that 
are renates but do not have hearts. Goodman would not agree, since, as he 
famously argues (1951: 5), 'the notion of "possible" cases, of cases that do 
not exist but might have existed, is far from clear' (see Counterfactual 
conditionals; Goodman, N. §3). But he and Quine would also be wary of talk of 
concepts generally; and semanticists such as Kaplan (1979) and Salmon (1986) 
are anxious to avoid introducing talk of them into talk of the semantics of 

Intensions as functions. Although one might agree that modal notions such as 
possibility and necessity are not as clear as one would like, it is by no means 
agreed that science can actually dispense with them. Many philosophers think 
that the laws essential to causal explanation in any science require modal and 
counterfactual talk. But, especially in psychology, it seems doubtful that 
extensions would perform all the explanatory work concepts are needed to 
perform. Whether or not biology need worry about the possibility of renates 
lacking hearts, someone could think something is a renate without thinking it 
has a heart. Consequently, many philosophers have claimed that, in addition to 
extensions, there must be 'intensions', or entities distinguished more finely 
than mere extensions permit (see Intensional entities; Intensional logics).

Intensions have been defined in a number of ways. One approach is in terms of 
senses or 'modes of presentation', to which we shall turn shortly (§5 below). 
Another approach simply amplifies the extensional characterization to include 
sets of possible as well as actual objects. Modal logicians and formal 
semanticists such as Montague (1974), D. Lewis (1972) and Stalnaker (1984), 
interested in presenting a formal account of the semantics of natural 
languages, have regarded intensions as functions that map a possible world to 
the extension of the concept in that world (see Semantics, possible worlds).

However, mere appeals to possibilia may still not cut things finely enough: for 
there are concepts that are different even though they apply to all the same 
things in all possible worlds, for example, [equiangular triangle] and 
[equilateral triangle], or, following Kripke ([1972] 1980), [water] and [H2O]; 
or, to take cases of necessarily empty extensions, [square circle] and [married 
bachelor], which both refer to nothing in all possible worlds. Particularly 
interesting examples of this latter category have been suggested by Kripke 
([1972] 1980) and Slote (1975), who argue in different ways that nothing could 
possibly satisfy the specific demands of [unicorn] or [monster]. How are we to 
distinguish these concepts by reference to possible objects?

Properties. Some philosophers think the appropriate reference for predicate 
concepts is not provided by the objects that the concepts pick out (whether in 
the actual or merely possible worlds), but rather by the properties those 
objects share. Thus, [city] is not individuated by the set of all actual or 
possible cities, but rather by the property, 'being a city.

Historically, concepts have not always been clearly distinguished from 
properties, both being regarded as 'universals' (see Universals). Thus, the 
mortality one found widespread among men was often assumed to be the same as 
the concept [mortality] that was a constituent of one's fears. Sometimes this 
identification seems terminological, as in Frege (1892a) (who uses 'concept' in 
a quite special way and discusses 'senses' independently), but at other times 
it is substantive, as in Carnap (1952). Most writers these days would 
distinguish the two (Putnam 1970; Bealer 1982), even if they also think that 
there is a property for every concept.

An interesting issue raised by Frege (1892a) that does seem common to both 
general concepts and properties is the difficulty of specifying exactly what 
sort of entities they are. As Frege noted, they seem to be incomplete, or 
'unsaturated', having places in them awaiting completion by objects, in the way 
that predicates in language, such as 'x loves y', have variables awaiting 
substitution with names (such as 'Romeo' and 'Juliet'). This issue becomes 
important when we try to specify how general and singular concepts combine to 
form a thought, or how properties and objects combine to constitute facts 
(Russell 1903: ch. 4; Wittgenstein 1921).

Many worry that appealing to properties to individuate concepts is gratuitous 
metaphysics, a free invention of a property for every concept, encouraged by 
the loose presumption that properties, such as 'immortality', can exist even 
without being instantiated. To answer this charge, philosophers often claim 
that properties are provided by the actual causal structure of the world: 
having kidneys and having a heart enter differently into causal relations, as 
perhaps do equiangularity and equilaterality (Sober 1982). Particularly 
philosophers of mind such as Dretske (1981, 1988), Millikan (1984) and Fodor 
(1991), interested in causal interactions between an organism and the world, 
find this way of thinking about concepts attractive (see Semantics, 
informational; Semantics, teleological).

However, it is not clear that causal properties will suffice. Are all our 
concepts really of causally efficacious properties? What about the concept [an 
inefficacious property]? Or concepts of secondary properties ([red], [sweet]), 
or ethics and aesthetics ([good], [comical]), which, many have argued, do not 
pick out genuine causal properties? Or consider, again, necessarily coextensive 
concepts such as [water] and [H2O] - which arguably correspond to the same 
property - or [round square] and [married bachelor], which arguably correspond 
to none. How could they differentially enter into the causal structure of the 
world? Or should we suppose that properties can be distinguished even though 
they are indistinguishable not only in the actual, but in all possible worlds? 
Are there any constraints?

Moreover, even if we could distinguish concepts by properties, that would not 
suffice for conceptual analysis. Plato's Euthyphro question - is something good 
because the gods love it, or do they love it because it is good? - brings this 
out nicely, since the question remains even if we assume that that gods love 
the good in all possible worlds (so that [good] and [god-beloved] are 
necessarily coextensive): the direction of analysis still needs to be 

5. Possession conditions: external v. internal

Many philosophers might not think that Plato's Euthyphro question needs an 
answer: for purposes of logic, and perhaps even formal semantics, appeal to any 
of these external phenomena (extensions, intensions or properties) may suffice, 
'analysis' be hanged. However, if concepts are to play a role in psychology, 
then one at least wants to know what sort of relation someone must bear to 
these external phenomena in order to qualify as a competent user of the 
concept. This is a question about the possession conditions for a concept to 
which many have thought analyses are crucial.

In considering possession conditions, special care is needed with the peculiar 
idiom 'concept of x' and the ontology it involves. Psychologists often speak of 
such things as the child's 'concept of causality'. This could mean the 
representation the child employs of the concept [causality] that the child 
shares with adults; or it could mean any of the extension, intension or rule 
that children associate with the English word 'cause'; or it could mean (as in 
fact it very often does mean) merely the standard beliefs - what some call the 
'conception' - that children associate with the extension, intension: 
[causality]. Which of these is intended all depends upon what entity one thinks 
of as the concept and what a mere accompaniment of it. What cannot be seriously 
intended is the suggestion that a child has a concept [causality] that is both 
identical to but different from the adults'. (What invites confusion here is 
the 'of' that implies no relation: just as 'the nation of China' means 'the 
nation, China', so 'the concept of x' often means 'the concept, [x]'.)

It might be thought that none of the external identifications of concepts could 
ever be viable for psychology, since psychology is about what is 'in the mind' 
(or 'in the head'), not what is in the world external to it (see Jackendoff 
1987: 126). This would be an error. We have already seen one way in which it 
cannot be true: in so far as concepts are shareable, they must be distinguished 
from individual mental episodes. But still it might be thought that a concept 
must be a type of internally specified mental state, since, after all, surely 
psychology aims to talk about individual minds, even if it categorizes them in 
various ways. However, an interest in characterizing what is going on in the 
mind need not exclude alluding to external objects: the fact that extensions or 
properties may be external to the head is no reason to think them unsuitable 
candidates for classifying things that are in the head, just as classifying 
various words in a book as 'about Vienna' does not prevent those words from 
existing entirely inside the book.

There have been a variety of external relations that philosophers have proposed 
that would link internal representations to external phenomena in a way that 
might constitute concept possession. Influential articles by Kripke ([1972] 
1980, 1982), Putnam (1975) and Burge (1979) have given rise to a variety of 
externalist theories of concepts, which look to such facts as actual causal 
history (Devitt 1981), various co-variation conditions (Dretske 1981, 1988; 
Fodor 1991) and evolutionary selection (Millikan 1984; Papineau 1987). However, 
in so far as they rely on real phenomena in the external world, they are 
subject to certain limitations that many feel can only be surmounted by 
appealing to some kind of conditions that are 'in the head'.

Intensions: 'senses'. What argues for the need for some internal condition on 
concept is the difficulty for any purely external account of capturing 
psychologically real distinctions. The examples of necessarily unextended 
concepts, such as [round square], suggest that the mind can somehow make 
distinctions for which there is no possible external reality. Consequently, 
many philosophers have argued that, in addition to the referent of a general 
term, there must also be (following Frege 1892b) its 'sense', or 'mode of 
presentation' (occasionally 'intension' is used here as well; see Sense and 
reference). Thus, what really seems to distinguish [equiangular triangles] and 
[equilateral triangles] is not the actual or possible things to which they 
refer, but rather the way the mind conceives them: it is one thing to think of 
something as (or qua) an equilateral triangle, another to think of it qua an 
equiangular triangle (which is why the proof that they are necessarily 
coextensive is informative). And this obviously helps with the problem of the 
necessarily coextensive: what distinguishes, for example, [water] and [H2O] are 
the different 'ways of thinking', not reflected in any even possible difference 
in the world. For some (for example, Peacocke 1992) concepts are senses so 
understood. But, of course, we then need a theory of senses.

6. The classical view and empiricism

One conception of senses is provided by the classical view of concepts. This 
view has two independent parts that are not always clearly distinguished, one 
making a claim about the nature of concepts, the other about what is to possess 
them: (a) concepts have an 'analysis' consisting of conditions that are 
necessary and sufficient for their satisfaction; and (b) these defining 
conditions are known to any competent user. An interesting, but problematic, 
example has been [knowledge], whose analysis was traditionally thought to be 
[justified true belief], but which has turned out to be far subtler, due to 
counterexamples raised by philosophers such as Gettier (1963) (see Knowledge, 
concept of).

The example of [knowledge] brings out an important caveat for the classical 
view: the proper analysis of a concept need not be readily available to a 
competent user of it. It was not easy for Athenians to reply to Plato's 
inquiries about [good], nor for recent philosophers to reply to Gettier. 
According to a reasonable version of the classical view, a competent user's 
knowledge of an analysis may be 'tacit' or 'unconscious', rather like the 
'knowledge' people have of the grammatical rules of their language, which they 
seem dependably to obey despite being unable to articulate them (see Evans 
1981; Katz 1971; Knowledge, tacit; Unconscious mental states). For Plato, the 
analyses could only be extracted from someone by a process of 'dialectic', 
involving consideration of various examples and arguments to a point of 
'reflective equilibrium' (Bealer 1987: 322; Jackson and Pettit 1995).

The classical view, however, has always had to face the difficulty of primitive 
concepts: how are they to be defined? An influential (but not the only 
possible) answer was provided by seventeenth-century British empiricists, who 
claimed that all the primitives were sensory. Indeed, the classical view has 
often been uncritically burdened with this further claim, or, anyway, the claim 
that all concepts are 'derived from experience'. Locke (1689), Berkeley (1710) 
and Hume (1739-40) seemed to take this to mean that concepts were somehow 
composed of introspectible mental items - images, 'impressions' - that were 
ultimately decomposable into basic sensory parts (see Empiricism; Sense-data).

Berkeley ([1710] 1982: 13) noticed a problem with this approach that every 
generation has had to rediscover: if a concept is a sensory impression, like an 
image, then how does one distinguish a general concept [triangle] from a more 
particular one - say, [isosceles triangle] - that would serve in imagining the 
general one? In any case, images seem quite hopeless for capturing the concepts 
associated with logical terms (what is the image for negation or for 
possibility?). Whatever the role of images, concepts and our competence with 
them involve something more (see Imagery).

Indeed, in addition to images and impressions and other sensory items, a full 
account of concepts needs to consider issues of logical structure. This is 
precisely what the logical positivists did, focusing on logically structured 
propositions and transforming the empiricist claim into their famous 
'verifiability theory of meaning': the meaning of a proposition is the means by 
which it is confirmed or refuted, ultimately by sensory experience; the concept 
expressed by a predicate is the statement of the (perhaps logically complex) 
sensory conditions under which people confirm or refute whether something 
satisfies it (see Meaning and verification). Thus, [acid] might be analysed by 
reference to tendencies to cause litmus paper to turn red; [belief] by 
observable behavioural dispositions (see Behaviourism, analytic); [material 
object] by enduring possibilities of sensation (see phenomenalism).

This once popular position has come under much attack in the last fifty years. 
Few, if any, successful 'reductions' of ordinary concepts (such as [material 
object], [cause]) to purely sensory concepts have ever been achieved, and there 
seems to be a pattern to the failures (Chisholm 1957). There have been four 
main diagnoses: (1) the classical search for 'necessary and sufficient' 
conditions is misguided and ought to be replaced by an appreciation of the role 
of a concept in our reasonings and theories of the world; (2) concepts should 
be regarded as 'family resemblance' structures, or 'prototypes', (3) because of 
the 'holism of confirmation', attempts to analyse concepts in terms of any 
verification conditions cannot succeed; and (4) we should stop looking for 
characterizations of concepts in terms of epistemic conditions, but rather, 
more metaphysically, in terms of the actual phenomena in the world to which 
people are referring, but about which they might be ignorant (thus, we would 
abandon clause (b) of the classical view, which requires analyses to be known 
by competent users). We will discuss each in turn.

7. Inferential roles and prototypes

Inferential roles. The first alternative, inspired by Wittgenstein's famous 
dictum, 'the meaning of a word is its use' (1953: §43), treats concepts as 
involving some or other role of a representation, either in a theory or in 
thought. Thus, many (for example, Kuhn 1962) have argued that someone possesses 
a concepts such as [witch] or [phlogiston] only if they understand the theories 
in which they play a role, or can reason with it in certain appropriate ways 
(see Semantics, conceptual role).

A vexing problem with this approach has been the fact that it is hard to 
identify just which roles are essential to a concept. It would appear that 
people can be wrong and/or disagree about almost anything: Berkeley claimed 
that material objects were ideas, some creationists that people are not 
animals, some nominalists that numbers are concrete objects. If people are 
genuinely to disagree with these views, they must share the relevant concepts; 
otherwise their use of the same words would be equivocal, their disagreement 
'merely verbal'. But then it seems very hard to insist upon any specific 
inferential role being essential to possessing a concept.

Prototypes. Another proposal also inspired by Wittgenstein (1953: §66) is to 
appeal to 'family resemblances' among the things to which a concept applies: he 
claimed that games, for example, share no single property, but are similar to 
each other in various ways that cluster together (some involve winning/losing, 
others mere entertainment; some are played in groups, others alone). This 
speculation was taken by psychologists (for example, Rosch 1973; Smith and 
Medin 1981) to be a testable psychological hypothesis. They showed that people 
respond differently (in terms of response time and other measures) to questions 
about whether, for example, penguins rather than robins are birds, in a fashion 
that suggested that concept membership was a matter not of possessing a 
classical analysis, but of distance from a 'prototype' or typical 'exemplar'. 
Thus, a robin satisfies many more of the features of a typical bird than does a 
penguin and so is a 'better' member of the category; and a malicious lie is a 
better case of a lie than a well-intentioned one.

It has not always been clear precisely what sort of thing a prototype or 
exemplar might be. One must take care not to import into the mind procedures, 
such as comparing one actual bird with another, that make sense only outside of 
it. Presumably either a prototype or an exemplar is some sort of representation 
(a list, or an 'image') indicating selected properties, and a metric for 
determining the distance of a candidate from those properties. Some writers 
have exploited the resources of 'fuzzy set theory' to capture the intended 
structure, whereby membership of a category is understood not as an 'all or 
none' affair, but as a matter of degree: everything satisfies every concept to 
some degree, however small (see Zadeh 1982; Fuzzy logic).

Quite apart from specifying just what the view involves, there are, however, a 
number of problems with appeals to prototypicality as a theory of concepts. In 
the first place, loosening the conditions on a concept's application from 
'defining' conditions to mere 'family resemblances' risks leaving that 
application far too unconstrained. Everything after all bears some resemblance 
to everything else (Goodman 1970): returning to Wittgenstein's example, 
anything, x, resembles standard games in some way or other (if only in 
belonging to some arbitrary set that contains all games and that thing x!). The 
question is which resemblances are essential to the concept, and which merely 
accidental - a question that returns us to the question the classical view 
tries to answer (see Essentialism).

Second, prototypes seem poor candidates for handling the crucial phenomenon of 
conceptual combination: the prototype for [tropical fish] does not seem 
constructible from the prototypes for [tropical] and [fish], yet someone could 
grasp [tropical fish] none the less (Osherson and Smith 1982).

Third, prototypicality, which presumably involves distances among a complex 
cluster of diverse properties, must be distinguished from both vagueness and 
estimation. As we have already observed (§1), nearly every concept admits of 
vague cases, in which it is not clear whether the concept applies. But this 
does not imply that the concept does not have a (correspondingly vague) 
definition. Similarly, estimation of whether or not something satisfies a 
concept is a question that arises with regard to any concept. But it is clearly 
not a metaphysical issue of the actual conditions something must satisfy in 
order to satisfy a concept, but rather an epistemological one concerning the 
belief or epistemic probability that something satisfies the conditions, given 
certain evidence (see Realism and antirealism). The sight of someone with a 
toupee may mean that there is a 90 per cent probability that he is actually 50 
per cent bald, or a 40 per cent probability that he is actually 95 per cent 
bald. The question of whether [bald] has a classical analysis is untouched by 
this issue as well (Rey 1983).

8. Metaphysics v. epistemology

These latter distinctions may turn on the different interests we have already 
noted (§1) in psychologists' and philosophers' use of 'concept', applying 
respectively to representations or to their shareable meanings. The fact that 
people are quicker to say that robins rather than penguins are birds may tell 
us something about people's representations of [bird], but nothing about the 
definition of the concept [bird] itself, that is, what is in fact required to 
satisfy that concept (on reflection, after all, most of us agree that penguins 
are bona fide birds, despite our initial hesitation). This is not to say that 
the definitional issue is not relevant to psychology: what people take to be 
required to be a bird is as much a psychological issue as how they figure out 
whether those requirements have been met. It is just that prototype theory 
seems to be addressed largely to the latter issue, the classical view to the 

However, the differences may be deeper than merely terminological. As the 
example of estimation shows, it is extremely easy to conflate metaphysical 
issues about the conditions for something's satisfying a concept with the 
epistemic ones of estimating whether something actually satisfies those 
conditions. One reason is that English can encourage running the two together, 
phrasing the metaphysical question as 'What determines what is what?' and the 
epistemic one as 'How does someone determine what is what?'. A second reason is 
that epistemic conditions are as likely to come to mind' in thinking with a 
concept as are its defining conditions (see §1 above).

But a more important reason is that empiricism made a policy of connecting the 
two: the defining conditions for a concept were to be stated in terms of 
experiential evidence. As anti-empiricists from Plato on have argued, however, 
many of our concepts seem to 'transcend experience', in that they seem to be 
graspable and sometimes applicable in the absence of it. For lack of any 
genuine Euclidean triangles in the world, it is unclear how our concept of them 
could be derived from experience. And even instantiated concepts such as 
[material object], [causation] and [prehistoric] seem to go far beyond mere 
sensory experience: we seem to be able to think coherently about material 
objects causally interacting in prehistoric times, even in the absence of any 
sensory evidence of that interaction. In any case, many of our concepts 
transcend their stereotypes: most of us understand the concept [female doctor], 
and recognize that [even number] has a perfectly good definition, despite our 
demonstrable reliance on stereotypes in both cases (Armstrong, Gleitman and 
Gleitman 1983).

Moreover, it can often seem arbitrary and unduly restrictive to tie a concept 
to any particular method of verification (or confirmation). Taking a page from 
Pierre Duhem (1914), Quine (1953) argued that 'our beliefs confront the 
tribunal of experience only as a corporate body': litmus paper turning red 
confirms that a solution is acidic only in conjunction with a great deal of 
background chemical and physical theory; indeed, Quine claims, only in 
conjunction with the whole of a person's system of beliefs (a view called 
'confirmation holism'; see Analyticity; Confirmation theory; Quine, W.V.). 
Hence, if a concept is to be analysed as its verification conditions, its 
meaning would be similarly holistic ('meaning holism'). Given that no two 
persons' beliefs are likely to be precisely the same, this has the consequence 
that no two people ever share precisely the same concepts - and no one could, 
strictly speaking, remember the same thing over any amount of time that 
included a change of any belief! Fodor and LePore (1992) have recently argued 
that this sort of conceptual (or semantic) holism would undermine serious 
psychology, but, fortunately, that the arguments for it are less than 
compelling (see Holism: mental and semantic; Atomism, ancient).

9. Difficulties for an internalist approach

Even if one distinguishes epistemological from metaphysical issues in 
determining concept identity, there remain a number of problems for any purely 
internalist theory of concepts. Whether classical or prototypical, any 
internalist theory of concepts requires distinguishing internal features - 
beliefs, inferential roles, prototypes - that are essential to (or defining of) 
a concept from those that are accidental, and many feel that it really is this 
distinction that is undermined by Quine's observations about holism. Indeed, 
'sameness of concept' for Quine becomes by and large an 'indeterminate' issue 
(see Radical translation and radical interpretation). The most one might expect 
is a similarity of inferential role between symbols in different theories or 
symbol systems (Harman 1972; Block 1986): which similarities are selected may 
vary for different explanatory tasks, and may be a pragmatic affair (Bilgrami 
1992; Lormand 1996).

A second problem emerged from the externalist approaches of Kripke ([1972] 
1980), Putnam (1975) and Burge (1979), and has come to be represented by 
Putnam's example of 'twin earth' (1975): suppose there were a planet exactly 
like the earth in every way except that, wherever the earth has H2O, twin earth 
has a different, but superficially similar chemical XYZ. Putnam argues that 
twin-earthlings would not mean by the word 'water' what we mean (for example, 
their tokens of the sentence 'Water is wet' would not have the same 
truth-conditions as ours), despite the fact that, ex hypothesi, twin-earthlings 
would have our same internal structure. (Burge (1979) and Stich (1983) present 
less outlandish examples.) As Putnam famously put it, 'meanings just ain't in 
the head'; rather, he argues, they depend at least in part upon the relations 
between internal states and external phenomena (see Content: wide and narrow).

In view of both these examples, and the Quinian worries, Fodor (1991, 1998) 
opts for an entirely 'atomistic' account of concepts, arguing that concepts 
have no 'analyses' whatsoever: they are simply ways in which people are 
directly related to individual properties in their environments, any one of 
which they might enjoy without the others. In principle, someone might have the 
concept [bachelor] and no other concepts at all, much less any 'analysis' of 
it, simply by virtue of having some internal state that is causally connected 
with bachelorhood in the local environment. Such a view goes hand in hand with 
Fodor's rejection of not only verificationist, but any empiricist, account of 
concept learning and construction. Indeed, given the failure of empiricist 
constructions, Fodor (1975, 1979) argues that concepts are not constructed or 
'derived from experience' at all, but are (nearly enough) all innate (see 
nativism). Devitt (1995) defends a more moderate, 'molecularist' position, 
allowing that many innate primitives are non-sensory (for example, [cause], 
[object]) but that others are susceptible to definition, especially in view of 
the thereby enlarged primitive base.

10. Two-factor theories and a modified classical view

Although externalism does seem to account both for the stability of concepts 
through variation in belief and for variations in concept due to variations in 
environment, it still must confront the issues we mentioned earlier (§5) that 
invite internalism, namely, that there seem to be more distinctions in the mind 
than are available in the external world. An increasingly popular approach is 
to separate the internal and external work concepts are asked to perform. 
According to 'two-factor' theories, 'concepts' should be regarded as having two 
components: one 'in the head', consisting of an internal representation playing 
a certain psychological role; and the other, some sort of co-variational law or 
evolutionary fact that, in a historical context, determines the reference and 
truth-conditions of the concept. (Sometimes 'concept' is restricted to the 
internal factor, 'content' to the external; and 'two-factor theory' is 
sometimes applied only to those views in which the two factors are relatively 
independent of one another.)

A two-factor theory leaves a place for a modified classical view, as well as 
for something like philosophical analysis. The internal factor would determine 
a full semantic content to a conceptual representation only in a particular 
context, so that the full analysis of (the content of) a concept might await 
empirical investigation of that context and not be available to its user. But 
this is perhaps as it should be: philosophical analysis of 'the nature of' a 
phenomenon may depend both upon the internal rule one is deploying and the 
actual phenomenon that, in a context, the rule picks out (Bealer 1987; Jackson 
and Pettit 1995).

See also: Content, non-conceptual; Semantics


References and further reading
Armstrong, S., Gleitman, L. and Gleitman, H. (1983) What Some Concepts Might 
Not Be', Cognition 13 (3): 263-308. (Discussion of experiments demonstrating 
prototypicality effects even with concepts, such as [even number], that have 
obvious classical definitions.)

Ayer, A.J. (1936) Language, Truth and Logic, London: Gollancz. (The classic 
defence of the logical positivist programme, including efforts to analyse all 
empirically meaningful statements into statements about possible sense 

Bealer, G. (1982) Quality and Concept, Oxford: Oxford University Press. (A 
recent effort to distinguish concepts from properties, and to provide a logical 
framework for discussing them both.)

Bealer, G. (1987) 'The Limits of Scientific Essentialism, in J. Tomberlin (ed.) 
Philosophical Perspectives, vol. 1, Metaphysics, Atascadero, CA: Ridgeview 
Press.(An argument that externalist theories of meaning and concepts must rely 
on certain internal conditions, knowable a priori.)

Berkeley, G. (1710) A Treatise concerning the Principles of Knowledge, 
Indianapolis, IN: Hackett Publishing Company, 1982.(Thirteen raises an 
important problem for an empiricism that derives 'ideas' too directly from 
sense 'impressions'.)

Bilgrami, A. (1992) Belief and Meaning: The Unity and Locality of Mental 
Content, Oxford: Blackwell.(A strategy for how meaning holism can be made 
compatible with interpersonal comparisons of meaning and concepts.)

Block, N. (1986) 'Advertisement for a Semantics for Psychology', in P.A. 
French, T.E. Uehling, Jr and H.K. Wettstein (eds) Midwest Studies in 
Philosophy, vol. 10, Studies in the Philosophy of Mind, Minneapolis, MN: 
University of Minnesota Press.(A defence of an inferential role theory of 
meaning and concepts as involving merely similarity, not identity among those 

Burge, T. (1979) 'Individualism and the Mental', in P.A. French, T.E. Uehling, 
Jr and H.K. Wettstein (eds) Midwest Studies in Philosophy, vol. 4, Minneapolis, 
MN: University of Minnesota Press. (Subtle defence of an externalist account of 
concept possession.)

Carnap, R. (1952) Fundamentals of Concept Formation in Empirical Science, 
Chicago, IL: University of Chicago Press.(Good example of a work in which 
concepts and properties are identified.)

Chisholm, R. (1957) Perceiving: A Philosophical Study, Ithaca, NY: Cornell 
University Press.(Classic critique of 'phenomenalist' and 'behaviourist' 
efforts to 'reduce' talk about material objects to talk about sensations, and 
talk about mental states to talk about external behaviour.)

Devitt, M. (1981) Designation, New York: Columbia University Press. (A defence 
of a causal theory of the reference of names - plausible as part of an 
externalist account of concepts of individuals.)

Devitt, M. (1995) Coming to Our Senses, Cambridge: Cambridge University Press. 
(A defence of a moderate conceptual molecularism, combining an externalist 
account of some non-sensory concepts, but also an inferential role account of 

Dretske, F. (1981) Knowledge and the Flow of Information, Cambridge, MA: MIT 
Press.(An effort to base an externalist theory of concepts on the notion of 

Dretske, F. (1988) Explaining Behavior: Reasons in a World of Causes, 
Cambridge, MA: MIT Press. (Further development of an informational semantics, 
linking informational roles to behavioural consequences.)

Duhem, P. (1914) The Aim and Structure of Physical Theory, trans. P. Wiener, 
New York: Atheneum, 1954. (Early statement of confirmation holism and, thereby, 
for an empiricist like Quine, for meaning, or conceptual, holism.).

Evans, G. (1981) 'Semantic Theory and Tacit Knowledge', in S. Holtzman and C. 
Leich (eds) Wittgenstein: To Follow a Rule, London: Routledge & Kegan Paul, 
118-37. (Discussion of the view that knowledge of the semantics of one's 
language might be tacit.)

Fodor, J.A. (1975) The Language of Thought, New York: Crowell. (Now classic 
statement of the claim that thought consists in computations on representations 
encoded in the brain, presumed throughout much cognitive psychology and in this 
entry; also, independently, initiates the argument that almost all concepts are 

Fodor, J.A. (1979) 'The Present Status of the Innateness Controversy', in 
RePresentations: Essays on the Foundations of Cognitive Science, Cambridge, MA: 
MIT Press.(Rich discussion of the issues underlying the claim that almost 
concepts are innate.)

Fodor, J.A. (1991) A Theory of Content, Cambridge, MA: MIT Press. (Vigorous 
defence of a radically externalist theory of meaning and concepts - although he 
tends to use the latter term for the internal representation of an externally 
determined 'content'.)

Fodor, J.A. (1998) Concepts: Where Cognitive Science Went Wrong, Oxford: Oxford 
University Press. (Extended critique of conceptual role and other analyses of 
concepts in current linguistics, philosophy and psychology.)

Fodor, J.A. and LePore, E. (1992) Holism: A Shoppers' Guide, Oxford: Blackwell. 
(A critique of arguments for semantic and conceptual holism.)

Frege, G. (1892a) 'Über Begriff und Gegenstand', Vierteljahrsschrift für 
wissenschaftliche Philosophie 16: 192-205; trans. P.T. Geach, 'On Concept and 
Object', in Translations from the Philosophical Writings of Gottlob Frege, ed. 
P.T. Geach and M. Black, Oxford: Blackwell, 3rd edn, 1980. (Frege himself used 
'concept' for something like what is more commonly called a 'property'; but the 
subtle issues he raises here apply to both.)

Frege, G. (1892b) 'Über Sinn und Bedeutung', Zeitschrift für Philosophie und 
philosophische Kritik 100: 25-50; trans. M. Black, 'On Sense and Reference', in 
Translations from the Philosophical Writings of Gottlob Frege, ed. P.T. Geach 
and M. Black, Oxford: Blackwell, 3rd edn, 1980. (Locus classicus of a 'sense' 
theory of meaning and what many regard as concepts.)

Gettier, E. (1963) 'Is Justified True Belief Knowledge?', Analysis 23: 
121-3.(Short and highly influential article presenting counterexamples to the 
traditional 'analysis' of [knowledge]; excellent as a paradigm of the 
philosopher's interest in concepts.)

Goodman, N. (1951) Structure of Appearance, Indianapolis, IN: Bobbs-Merrill, 
1966.(A classic effort at empiricist analysis of objective into sensory 
concepts, wholly within an extensional conception.)

Goodman, N. (1970) 'Seven Strictures on Similarity', in L. Foster and J. 
Swanson (eds) Experience and Theory, Amherst, MA: University of Massachusetts 
Press.(Excellent discussion of the perils of appealing to 'similarity' in 
theories of concepts.)

Grice, H.P. (1957) 'Meaning', Philosophical Review 66: 377-88. (Classic sketch 
of a programme for deriving the meaning of sentences from the intentions of 

Harman, G. (1972) Thought, Princeton, NJ: Princeton University Press. (Defence 
of an inferential role theory of meaning and concepts as involving merely 
similarity, not identity among those roles.)

Hume, D. (1739-40) A Treatise of Human Nature, ed. L.A. Selby-Bigge, revised 
P.H. Nidditch, Oxford: Clarendon Press, 1975. (Classic development of an early 
empiricist theory of concepts.)

Jackendoff, R. (1987) Consciousness and Computation, Cambridge, MA: MIT Press. 
(Lively and imaginative internalist account of conceptual structure as it 
appears to be revealed by the semantics of natural language.)

Jackson, F. and Pettit, P. (1995) 'Moral Foundationalism and Moral Motivation', 
Philosophical Quarterly 45 (178): 20-40. (Recent 'two-factor proposal to 
provide definitions by the role of terms in ordinary thought, which, given a 
context of utterance, determines a propositional content.)

Kant, I. (1781/1787) Critique of Pure Reason, trans. N. Kemp Smith, New York: 
St. Martin's Press, 1968. (Classic study of the basic concepts arguably 
required for any understanding of an objective world.)

Kaplan, D. (1979) 'Dthat', in P. French, T. Uehling and H. Wettstein (eds) 
Contemporary Studies in the Philosophy of Language, Minneapolis, MN: University 
of Minnesota Press, 383-400. (Highly influential development of a 'direct 
reference' theory of demonstratives (for example, 'that', 'this'), indexicals 
('I', 'her') and other expressions, according to which 'concepts' play much 
less of a role than traditionally supposed.)

Katz, J. (1971) The Underlying Reality of Language and its Philosophical 
Import, New York: Harper & Row. (Early proposal modelling knowledge of 
semantics and concepts on the kind of tacit knowledge of syntax postulated by 

Katz, J. (1972) Semantic Theory, New York: Harper & Row. (Defence of the 
classical view on behalf of a semantics of natural language.)

Kripke, S.A. (1972) 'Naming and Necessity', in D. Davidson and G. Harman (eds) 
Semantics of Natural Language, Dordrecht: Reidel, 252-355; expanded version 
published as Naming and Necessity, Oxford and New York: Blackwell, 1980.(One of 
the original defences of an externalist account of proper names and natural 
kind terms; suggestive of a similar account of the corresponding concepts.)

Kripke, S.A. (1982) Wittgenstein on Rules and Private Language, Cambridge, MA: 
Harvard University Press.(An attack on an internalist account of concept 
possession, and a suggestion of an externalist 'social' theory instead.)

Kuhn, T. (1962) The Structure of Scientific Revolutions, Chicago, IL: 
University of Chicago Press.(Influential defence of a holistic, inferential 
role theory of concept possession.)

Laurence, S. and Margolis, E. (eds) (1998) Concepts, Cambridge, MA: MIT Press. 
(An excellent collection of leading articles on the topic by philosophers, 
psychologists and logicians.)

Lewis, D.K. (1972) 'General Semantics', in D. Davidson and G. Harman (eds) 
Semantics of Natural Language, Dordrecht: Reidel. (Systematic presentation of a 
theory of meaning and concepts as intension-functions on possible worlds.)

Locke, J. (1689) An Essay concerning Human Understanding, New York: Dutton 
(Everyman), 1961.(The original proposal of an empiricist theory of concepts.)

Lormand, E. (1996) 'How to Be a Meaning Holist', Journal of Philosophy 93: 
51-73.(Defence of the view that a token representation may have many different 
meanings, for different explanatory purposes.)

Millikan, R. (1984) Language, Thought and Other Biological Categories, 
Cambridge, MA: MIT Press.(The original statement of an 
evolutionary/teleological theory of meaning and concepts.)

Montague, R. (1974) Formal Philosophy, ed. R. Thomason, New Haven, CT: Yale 
University Press.(A systematic development of a theory of meaning and concepts 
as intension-functions on possible worlds.)

Osherson, D. and Smith, E. (1982) 'Gradedness and Conceptual Combination', 
Cognition 12: 299-318. (Examination of the difficulties of conceptual 
combination for prototype theories.)

Papineau, D. (1987) Reality and Representation, Oxford: Blackwell. (Defence of 
an evolutionary approach to concept ascription.)

Peacocke, C. (1992) A Study of Concepts, Cambridge, MA: MIT Press. 
(Sophisticated and influential defence of a 'sense' theory of concepts.)

Plato (395-347 BC) Euthyphro, in The Collected Dialogues of Plato including the 
Letters, ed. E. Hamilton and H. Cairns, Princeton, NJ: Princeton University 
Press, 1961.(Raises an important kind of question for conceptual analysis: is 
something good because the gods love it, or do they love it because it is 

Putnam, H. (1970) 'On Properties', in Philosophical Papers, vol. 1, Cambridge: 
Cambridge University Press, 1975, 305-22. (Excellent discussion distinguishing 
properties from concepts.)

Putnam, H. (1975) 'The Meaning of "Meaning", in Philosophical Papers, vol. 2, 
Mind, Language, and Reality, Cambridge: Cambridge University Press. (Highly 
influential, lively and readable defence of an 'externalist' theory of meaning 
and concepts.)

Quine, W.V. (1953) 'Two Dogmas of Empiricism', in From a Logical Point of View 
and Other Essays, Cambridge, MA: Harvard University Press. (Important source of 
attacks on the scientific significance of conceptual analysis and on the 
classical view.)

Quine, W.V. (1954) 'Carnap and Logical Truth', in Ways of Paradox and Other 
Essays, Cambridge, MA: Harvard University Press, 2nd edn, 1976. (Superb essay 
on the history of 'conceptual analysis', as well as important arguments on 
behalf of his meaning holism and against the scientific significance of 

Quine, W.V. (1960) Word and Object, Cambridge, MA: MIT Press. (Classic 
exposition of an account of mind and language without appeals to concepts or 

Rey, G. (1983) 'Concepts and Stereotypes', Cognition 15: 237-62; repr. in S. 
Laurence and E. Margolis (eds) Concepts, Cambridge, MA: MIT Press, 
1998.(Criticism of prototype theories for conflating epistemological with 
metaphysical issues.)

Rey, G. (forthcoming) 'A Naturalistic A Priori', Philosophical Studies.(Argues 
that the classical view can be defended against Quinian attacks by supposing 
analyses are sub-doxastic, like the rules of grammar.)

Rips, L. (1995) 'The Current Status of Research on Concept Combination', Mind 
and Language 10 (1/2): 72-104. (Excellent review of psychological research on 
concepts to that date.)

Rosch, E. (1973) 'On the Internal Structure of Perceptual and Semantic 
Categories', in T.E. Moore (ed.) Cognitive Development and Acquisition of 
Language, New York: Academic Press. (Influential discussion of the role of 
'prototypes' in categorization tasks.)

Russell, B. (1903) Principles of Mathematics, New York: Norton, 2nd edn, 1938. 
(Chapter 4 wrestles with the problem of distinguishing a sentence from mere 
lists of words, which involves thinking about how a general concept is related 
to the individual (concept?) that satisfies it; connected to discussions in 
Frege (1892a) and Wittgenstein (1921).)

Russell, B. (1956) Logic and Knowledge, Essays 1901-1950, ed. R.C. Marsh, 
London: Allen & Unwin; repr. London: Routledge, 1992. (Influential essays 
presenting a highly 'referential' conception of the constituents of thoughts 
and propositions.)

Salmon, N. (1986) Frege's Puzzle, Cambridge, MA: MIT Press/Bradford Books. 
(Argues against 'sense' theories of linguistic meaning.)

Slote, M. (1975) 'Necessarily Inapplicable Concepts', Philosophical Studies 28: 
265-71.(Argues that certain familiar concepts, such as [miracle] and [evil], 
could not possibly be instantiated.)

Smith, E. and Medin, D. (1981) Concepts and Categories, Cambridge, MA: Harvard 
University Press.(Useful discussion of psychological research supporting 
prototype theories.)

Sober, E. (1982) 'Why Logically Equivalent Predicates May Pick Out Different 
Properties', American Philosophical Quarterly 19: 183-9. (Argues that 
predicates such as 'equiangular' and 'equilateral' may pick out not only 
different concepts, but also different properties.)

Stalnaker, R. (1984) Inquiry, Cambridge, MA: MIT Press/Bradford Books. (Clear 
and readable defence of a theory of meaning and concepts as intension-functions 
on possible worlds.)

Stich, S. (1983) From Folk Psychology to Cognitive Science: The Case Against 
Belief, Cambridge, MA: MIT Press.(Proposes an essentially pragmatic approach to 
concept ascription across people; good discussion of intuitions leading us to 
different descriptions.)

Wittgenstein, L. (1921) Tractatus Logico-Philosophicus, trans. D.F. Pears and 
B.F. McGuinness, London: Routledge & Kegan Paul, 1961. (Proposes an interesting 
'picture' theory of meaning to solve the problem of how predicates combine with 
names to form sentential representations; suggestive of a similar treatment of 
mental representations and/or concepts.)

Wittgenstein, L. (1953) Philosophical Investigations, New York: Macmillan. (The 
source of use and 'inferential role' theories of concept possession, as well as 
of the suggestion that concepts might have a prototype or 'family resemblance' 

Zadeh, L. (1982) 'A Note on Prototype Theory and Fuzzy Sets', Cognition 12: 
291-7.(Application of the formalism of 'fuzzy set theory' to a prototype theory 
of concepts.)

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