Kent Bach, Routledge Encyclopedia of Philosophy
A word, phrase, or sentence is ambiguous if it has more than one meaning. The word 'light', for example, can mean not very heavy or not very dark. Words like 'light', 'note', 'bear' and 'over' are lexically ambiguous. They induce ambiguity in phrases or sentences in which they occur, such as 'light suit' and 'The duchess can't bear children'. However, phrases and sentences can be ambiguous even if none of their constituents is. The phrase 'porcelain egg container' is structurally ambiguous, as is the sentence 'The police shot the rioters with guns'. Ambiguity can have both a lexical and a structural basis, as with sentences like 'I left her behind for you' and 'He saw her duck'.
The notion of ambiguity has philosophical applications.
For example, identifying an ambiguity can aid in solving a philosophical
problem. Suppose one wonders how two people can have the same idea, say
of a unicorn. This can seem puzzling until one distinguishes 'idea' in the
sense of a particular psychological occurrence, a mental representation,
from 'idea' in the sense of an abstract, shareable concept. On the other
hand, gratuitous claims of ambiguity can make for overly simple solutions.
Accordingly, the question arises of how genuine ambiguities can be distinguished
from spurious ones. Part of the answer consists in identifying phenomena
with which ambiguity may be confused, such as vagueness, unclarity, inexplicitness
1. Types of ambiguity
2. Ambiguity contrasted
3. Philosophical relevance
1. Types of ambiguity
Although people are sometimes said to be ambiguous in how they use language, ambiguity is, strictly speaking, a property of linguistic expressions. A word, phrase, or sentence is ambiguous if it has more than one meaning. Obviously this definition does not say what meanings are or what it is for an expression to have one (or more than one). For a particular language, this information is provided by a grammar, which systematically pairs forms with meanings, ambiguous forms with more than one meaning (see MEANING and SEMANTICS).
There are two types of ambiguity, lexical and structural. Lexical ambiguity is by far the more common. Everyday examples include nouns like 'chip', 'pen' and 'suit', verbs like 'call', 'draw' and 'run', and adjectives like 'deep', 'dry' and 'hard'. There are various tests for ambiguity. One test is having two unrelated antonyms, as with 'hard', which has both 'soft' and 'easy' as opposites. Another is the conjunction reduction test. Consider the sentence, 'The tailor pressed one suit in his shop and one in the municipal court'. Evidence that the word 'suit' (not to mention 'press') is ambiguous is provided by the anomaly of the 'crossed interpretation' of the sentence, on which 'suit' is used to refer to an article of clothing and 'one' to a legal action.
The above examples of ambiguity are each a case of one word with more than one meaning. However, it is not always clear when we have only one word. The verb 'desert' and the noun 'dessert', which sound the same but are spelled differently, count as distinct words (they are homonyms). So do the noun 'bear' and the verb 'bear', even though they not only sound the same but are spelled the same. These examples may be clear cases of homonymy, but what about the noun 'respect' and the verb 'respect' or the preposition 'over' and the adjective 'over'? Are the members of these pairs homonyms or different forms of the same word? There is no general consensus on how to draw the line between cases of one ambiguous word and cases of two homonyous words. Perhaps the difference is ultimately arbitrary.
Sometimes one meaning of a word is derived from another. For example, the cognitive sense of 'see' seems derived from its visual sense. The sense of 'weigh' in 'He weighed the package' is derived from its sense in 'The package weighed two pounds'. Similarly, the transitive senses of 'burn', 'fly' and 'walk' are derived from their intransitive senses. Now it could be argued that in each of these cases the derived sense does not really qualify as a second meaning of the word but is actually the result of a lexical operation on the underived sense. This argument is plausible to the extent that the phenomenon is systematic and general, rather than peculiar to particular words. Lexical semantics has the task of identifying and characterizing such systematic phemena. It is also concerned to explain the rich and subtle semantic behavior of common and highly flexible words like the verbs 'do' and 'put' and the prepositions 'at', 'in' and 'to'. Each of these words has uses which are so numerous yet so closely related that they are often described as 'polysemous' rather than ambiguous.
Structural ambiguity occurs when a phrase or sentence has more than one underlying structure, such as the phrases 'Tibetan history teacher', 'a student of high moral principles' and 'short men and women', and the sentences 'The girl hit the boy with a book' and 'Visiting relatives can be boring'. These ambiguities are said to be structural because each such phrase can be represented in two structurally different ways, e.g., '[Tibetan history] teacher' and 'Tibetan [history teacher]'. Indeed, the existence of such ambiguities provides strong evidence for a level of underlying syntactic structure (see SYNTAX). Consider the structurally ambiguous sentence, 'The chicken is ready to eat', which could be used to describe either a hungry chicken or a broiled chicken. It is arguable that the operative reading depends on whether or not the implicit subject of the infinitive clause 'to eat' is tied anaphorically to the subject ('the chicken') of the main clause.
It is not always clear when we have a case of structural ambiguity. Consider, for example, the elliptical sentence, 'Perot knows a richer man than Trump'. It has two meanings, that Perot knows a man who is richer than Trump and that Perot knows man who is richer than any man Trump knows, and is therefore ambiguous. But what about the sentence 'John loves his mother and so does Bill'? It can be used to say either that John loves John's mother and Bill loves Bill's mother or that John loves John's mother and Bill loves John's mother. But is it really ambiguous? One might argue that the clause 'so does Bill' is unambiguous and may be read unequivocally as saying in the context that Bill does the same thing that John does, and although there are two different possibilities for what counts as doing the same thing, these alternatives are not fixed semantically. Hence the ambiguity is merely apparent and better described as semantic underdetermination.
Although ambiguity is fundamentally a property of
linguistic expressions, people are also said to be ambiguous on occasion
in how they use language. This can occur if, even when their words are unambiguous,
their words do not make what they mean uniquely determinable. Strictly speaking,
however, ambiguity is a semantic phenomenon, involving linguistic meaning
rather than speaker meaning (see MEANING AND COMMUNICATION);
'pragmatic ambiguity' is an oxymoron. Generally when one uses ambiguous
words or sentences, one does not consciously entertain their unintended
meanings, although there is psycholinguistic evidence that when one hears
ambiguous words one momentarily accesses and then rules out their irrelevant
senses. When people use ambiguous language, generally its ambiguity is not
intended. Occasionally, however, ambiguity is deliberate, as with an utterance
of 'I'd like to see more of you' when intended to be taken in more than
one way in the very same context of utterance.
2. Ambiguity contrasted
It is a platitude that what your words convey 'depends on what you mean'. This suggests that one can mean different things by what one says, but it says nothing about the variety of ways in which this is possible. Semantic ambiguity is one such way, but there are others: homonymy (mentioned above), vagueness, relativity, indexicality, nonliterality, indirection and inexplicitness. All these other phenomena illustrate something distinct from multiplicity of linguistic meaning.
An expression is vague if it admits of borderline cases (see VAGUENESS). Terms like 'bald', 'heavy' and 'old' are obvious examples, and their vagueness is explained by the fact that they apply to items on fuzzy regions of a scale. Terms that express cluster concepts, like 'intelligent', 'athletic' and 'just', are vague because their instances are determined by the application of several criteria, no one of which is decisive.
Relativity is illustrated by the words 'heavy' and 'old' (these are vague as well). Heavy people are lighter than nonheavy elephants, and old cats can are younger than some young people. A different sort of relativity occurs with sentences like 'Jane is finished' and 'John will be late'. Obviously one cannot be finished or late simpliciter but only finished with something or late for something. This does not show that the words 'finished' and 'late' are ambiguous (if they were, they would be ambiguous in as many ways as there are things one can be finished with or things one can be late for), but only that such a sentence is semantically underdeterminate--it must be used to mean more than what the sentence means.
Indexical terms, like 'you', 'here' and 'tomorrow', have fixed meaning but variable reference. For example, the meaning of the word 'tomorrow' does not change from one day to the next, though of course its reference does (see DEMONSTRATIVES AND INDEXICALS).
Nonliterality, indirection and inexplicitness are
further ways in which what a speaker means is not uniquely determined by
what his words mean (see SPEECH ACTS). They can give
rise to unclarity in communication, as might happen with utterances of 'You're
the icing on my cake', 'I wish you could sing longer and louder', and 'Nothing
is on TV tonight'. These are not cases of linguistic ambiguity but can be
confused with it because speakers are often said to be ambiguous.
3. Philosophical relevance
Philosophical distinctions can be obscured by unnoticed ambiguities. So it is important to identify terms that do doubtle duty. For example, there is a kind of ambiguity, often described as the 'act/object' or the 'process/product' ambiguity, exhibited by everyday terms like 'building', 'shot' and 'writing'. Confusions in philosophy of language and mind can result from overlooking this ambiguity in terms like 'inference', 'statement' and 'thought'. Another common philosophical ambiguity is the type/token distinction. Everyday terms like 'animal', 'book' and 'car' apply both to types and to instances (tokens) of those types. The same is true of linguistic terms like 'sentence', 'word' and 'letter' and to philosophically important terms like 'concept', 'event' and 'mental state' (see TYPE/TOKEN DISTINCTION).
Although unnoticed ambiguities can create philosophical problems, ambiguity is philosophically important also because philosophers often make spurious claims of it. Indeed, the linguist Charles Ruhl has argued that certain ostensible ambiguities, including act/object and type/token, are really cases of lexical underdetermination. Saul Kripke laments the common strategem, which he calls 'the lazy man's approach in philosophy', of appealing to ambiguity to escape from a philosophical quandary, and H. P. Grice urges philosophers to hone the 'Modified Occam's Razor: senses are not to be multiplied beyond necessity'. He illustrates its value by shaving a sense off the logical connective 'or', which is often thought to have both an inclusive and exclusive sense. Grice argues that, given its inclusive meaning, its exclusive use can be explained entirely on pragmatic grounds (see IMPLICATURE). Another example, prominent in modern philosophy of language, is the ambiguity alleged to arise from the distinction between referential and attributive uses of definite descriptions (see DESCRIPTIONS). Less prominent but not uncommon is the suggestion that pronouns are ambiguous as between their anaphoric and their deictic use (see PRONOUNS AND ANAPHORA). So, for example, it is suggested that a sentence like 'Oedipus loves his mother' has two 'readings', i.e., is ambiguous, because it can be used to mean either that Oedipus loves his own mother or that Oedipus loves the mother of some contextually specified male. However, this seems to be an insufficient basis for the claim of ambiguity. After all, being previously mentioned is just another way of being contextually specified. Accordingly, there is nothing semantically special in this example about the use of 'his' to refer to Oedipus.
Claims of structural ambiguity can also be controversial. Of particular importance are claims of scope ambiguity, which are commonly made but rarely defended. A sentence like 'Everybody loves somebody' is said to exhibit a scope ambiguity because it can be used to mean either that for each person, there is somebody that that person loves or (however unlikely) that there is somebody that everybody loves. These uses may be represented, respectively, by the logical formulas '("x)(Ey)(Lxy)' and '(Ey)("x)(Lxy)'. It is generally assumed that because different logical formulas are needed to represented the different ways in which an utterance of such a sentence can be taken, the sentence itself has two distinct logical forms (see LOGICAL FORM). Sustaining this claim of ambiguity requires identifying a level of linguistic description at which the sentence can be assigned two distinct structures. Some grammarians have posited a level of LF, corresponding to what philosophers call logical form, at which relative scope of quantified noun phrases may be represented. However, LF of this kind does not explain scope ambiguities that philosophers attribute to sentences containing modal operators and psychological verbs, such as 'The next president might be a woman' and 'Ralph wants a sloop' (see SCOPE). An utterance of such a sentence can be taken in either of two ways, but it is arguable that the sentence is not ambiguous but merely semantically underdeterminate with respect to its two alleged 'readings'.
Notwithstanding the frequency in philosophy of unwarranted and often arbitrary claims of ambiguity, it cannot be denied that some terms really are ambiguous. The nouns 'bank' and 'suit' are clear examples, and so are the verbs 'bank' and 'file'. Philosophers sometimes lament the prevalence of ambiguity in natural languages and yearn for an ideal language in which it is absent. But ambiguity is a fact of linguistic life. Despite the potentially endless supply of words, many words do double duty or more. And despite the unlimited number of sentences, many have several meanings, and their utterance must be disambiguated in light of the speaker's likely intentions.
References and further reading
Atlas, J. D. (1989) Philosophy without Ambiguity: A Logico-Linguistic Essay, Oxford: Oxford University Press. (Examines ambiguity tests and questions certain philosophical appeals to ambiguity.)
Bach, K. (1994) 'Conversational impliciture', Mind & Language 9: 124-62. (Identifies ways, distinct from those identified by Grice, in which linguistic meaning can underdetermine speaker meaning and, in particular, contrasts semantic underdetermination with ambiguity.)
Cruse, D. A. (1986) Lexical Semantics, Cambridge, Eng.: Cambridge University Press, pp. 49-68. (Discusses linguistic features of ambiguity and examines tests for it.)
* Grice, H. P. (1967) 'Logic and conversation', published as chapter 2 of Studies in the Way of Words (1989), Cambridge, Mass.: Harvard University Press. (Explains how multiple uses of an expression can often be explained without appealing to ambiguity.)
* Kripke, S. (1977) 'Speaker's reference and semantic reference', Midwest Studies in Philosophy 2: 255-76. (A case study, focussing on the distinction between referential and attributive uses of definite descriptions (see DESCRIPTIONS), in how to expose a gratuitous philosophical claim of ambiguity.)
May, R. (1985) Logical Form: Its Structure and Derivation. Cambridge, Mass.: MIT Press (Investigates the hypothesis within generative grammar that there is a level of representation, Logical Form.)
* Ruhl, C. (1989) On Monosemy: A Study in Linguistic Semantics, Albany: State University of New York Press. (Argues for the presumption that a word has a single, though highly abstract, meaning rather than the multiplicity of meanings commonly attributed, as by the list of definitions in its dictionary entry.)
Zwicky, A. and J. Sadock (1975) 'Ambiguity tests and how to fail them', in J. Kimball (ed.) Syntax and Semantics 4, New York: Academic Press. (Presents and assesses various linguistic tests of ambiguity.)