Legal Theory Lexicon 051: Vagueness and Ambiguity

Introduction

This week the Legal Theory Lexicon entry focuses on "ambiguity" and "vagueness"--two important concepts for the theory of interpretation.  Some legal texts are ambiguous--they contain words or phrases that can have two or more distinct meanings.  And some legal texts are vague--they use concepts that have indefinite application to particular cases.  And some legal texts are both vague and ambiguous--they have multiple meanings, some (or all) of which have indefinite applications.  Because "vagueness" and "ambiguity" are basic concepts in the theory of interpretation, its important to master each of them and to understand the difference between them.

As always, this entry in the Legal Theory Lexicon is aimed at law students, especially first year law students, with an interest in legal theory.

Vagueness  

What does it mean to say that a concept, term, or phrase is vague?  Let's start with some examples and then try for an elucidation of the concept.  "Tall" is a good example of a vague concept.  Some humans are definitely not tall--Danny DeVito, for example.  Others definitely are tall--Boban Marjanović, for one.  But the term "tall" is vague.  5'11 is almost definitely tall for a woman in the United Sates, but might be a borderline case for men.  "Tall" is not the sort of quality for which there are definite criteria that sort the world into "tall" things and "not tall" things.  In other words, "tall" is vague.

There are lot's of terms that are like tall: short, strong, weak, heavy, light, warm, and cool--all of these are terms that seem to have borderline cases.  And that is one way that we might define vagueness.  A term is vague, we might say, if and only if it has borderline cases.  A term is not vague just in case it has no borderline cases.

As you might guess, the fact of vagueness creates a variety of issues in the philosophy of language.  Is vagueness built into the fabric of the universe?  Or is vagueness merely a feature of the imprecision of human language?  Is vagueness a property of things?  Or is it a property of our knowledge of things?  We won't worry about these deep questions.  For the purposes of this rough and ready introduction, it is sufficient simply to see that there are such problems and that a philosophical theory of vagueness should propose to answers to them or show that they aren't true problems at all.

Ambiguity  

What about "ambiguity"?  A word or phrase is ambiguous if it has more than one meaning.  Take "cool" for example.  One meaning of "cool" has to do with temperature, and in this sense, "cool" contrasts with "warm," "cold," and "hot."  Another meaning of "cool" has to do with fashion and social attractiveness.  And there are other senses of "cool" as well, as in, he kept his cool in a very pressured situation.  So, the word "cool" is ambiguous because it has multiple senses, with each sense representing a different concept.

In a particular context, the meaning of an ambiguous term may be clear.  In the sentence "He's one cool dude," the word "cool" is likely to refer to social attractiveness and not temperature.  By considering the word "cool" in the context of the whole sentence, we are able to disambiguate and identify the relevant sense of "cool."  But in some contexts, the ambiguity may be difficult to resolve: "The aviation is a cool drink" could refer either to the fact that aviations are served chilled but not icee cold or to the fact that aviations are fashionable and popular among some social groups.

And this last example, "cool" can be used to illustrate the fact that the same term can be both vague and ambiguous in the same context.  If I say, "Bring me a cool drink!", my utterance may be both ambiguous--do I mean fashionable or coldish?--and vague--how far below room temperature is "cool" or are aviations still "cool" or are they now "out of style"?

Interpretation of Vague or Ambiguous Texts 

Now that we have a basic grasp of vagueness and ambiguity, we are in a position to see that each of these two concepts has a role to play in a theory of the interpretation of legal texts.

Many legal texts are vague.  In fact, most law students become very familiar with a variety of vague terms early in their law school careers.  Take "reasonable"--was the tort defendant's conduct "reasonable" under the circumstances?  There will be clear cases of unreasonable conduct: driving 150 mph in a residential area.  But there will also be borderline cases.  Was it reasonable to drive at 55 mph in a light fog?

Some legal language general, abstract, and vague.  For example, the phrase "equal protection" in the 14th amendment of the United States Constitution might refer to a very general and abstract idea of equality.  Given this generality and abstraction, it might be that the "borderline" cases seem to make up the whole of equal protection doctrine.  What would count as a clear example of "equal" or of "unequal"?  In a common law system, general and abstract language may be translated into relatively more particular and concrete rules through case-by-case adjudication.

Vagueness is ubiquitous in the law, and frequently legal actors (courts and others who apply the law) must resolve borderline cases.  Every law student is familiar with the strategies that are employed, which include case-by-case balancing tests, supplementary doctrines that provide bright-line rules to implement vague legal texts, and so forth.

Ambiguity may be less common, because many potentially ambiguous terms or phrases are disambiguated by context.  "Seizure" can refer to a physical taking or it can refer to a medical symptom, but in the Fourth Amendment of the United States Constitution, it is clear that the correct meaning is the former rather than the latter.

Beyond Vagueness and Ambiguity

Both vagueness and ambiguity can be viewed as forms of underdetermination: the communicative content of a legal text cannot fully determine the legal effect of the text if the communicative content is vague or irreducibly ambiguous.  But there may be other forms of underdetermination.  Some texts may be "open textured" and others may have multidimensional content with dimensions that are incommensurable.  And there may be other forms of underdetermination as well.  These phenomena require their own Lexicon entry.

Relationship to the Interpretation-Construction Distinction

The distinction between vagueness and ambiguity is related to the interpretation-construction distinction--discussed in a separate entry in the Legal Theory Lexicon.  Roughly, the distinction is that interpretation of a text aims at recovering its linguistic meaning or semantic content. Construction involves the "tranlation" of the semantic content into legal content: we we construe a legal text we formulating legal rules that enable application of the text to particular cases.

Interpretation and Ambiguity--In many cases, problems of interpretation involve ambiguity: a legal text uses a word with more than one meaning and the interpreter looks to context to resolve the ambiguity.

Construction and Vagueness--But when a text is vague, it is usually the case that interpretation cannot resolve the vagueness.  Why not?  Because interpretation only can take us as far as the meaning of the text: if the linguistic meaning is vague, then something else will be required if we must apply the text to a particular case.  Construction allows legal actors (e.g., judges) to devise a supplementary rule or procedure that resolves the vagueness.  Thus, a legal text may supply a vague standard ("freedom of speech"), but construction may yield a more particular rule ("no prior restraints").  (There is a Lexicon entry on rules, standards, and principles.)

An Example: Ambiguity and Vagueness in Chevron

Why is the ambiguity-vagueness distinction important?  Does the distinction make any practical difference?  We can approach these questions via an exploration of the role of the word "ambiguity" in the famous Supreme Court decision in Chevron U.S.A., Inc. v. Natural Resources Defense Council, Inc., the case that gave rise to what is called the "Chevron Doctrine."  In a super-simplified nutshell, the Chevron Doctrine requires courts to defer to "interpretations" of statutes by administrative agencies when a statute is "ambiguous."  But as Professor Cass Sunstein and I show in an article entitled "Chevron as Construction," the Chevron case itself actually involved a provision that was vague or open-textured.  The problem in Chevron wasn't that some word or phrase in the statute had multiple sense, but instead involved an agency making a judgment about how to precisfy an underdeterminate provision.  Then, decisions subsequent to Chevron extended the doctrine to cases in which the language of the statute was ambiguous (multiple senses).  Much of the criticism of Chevron focuses on these cases, where deference to the agency seems inconsistent with the traditional notion that statutory interpretation (determinations of meaning) is the province of judges and not administrative agencies.

Conclusion

"Vagueness" and "ambiguity" are important concepts in the theory of legal interpretation generally, and as a consequence, they are important to constitutional theory and the theory of statutory interpretation.  I hope this Lexicon entry has clarified the distinction between these two concepts.

Related Lexicon Entries

• Legal Theory Lexicon 063: Interpretation and Construction

Resources on the Internet

• Lawrence B. Solum & Cass R. Sunstein, Chevron as Construction, 105 Cornell Law Review 1465 (2020). 
• Roy Sorensen, Vagueness, Stanford Encyclopedia of Philosophy (2006).
• Adam Sennett, Ambiguity, Stanford Encyclopedia of Philosophy (2011).
• Dominic Hyde, Sorites Paradox, Stanford Encyclopedia of Philosophy (2005).
• Wikipedia Article on Vagueness
• Vagueness in Law by Timothy A. O. Endicott

Bibliography

• Timothy A.O. Endicott, Vagueness in Law  (Oxford University Press, 2001)
• Cuts and Clouds: Vaguenesss, its Nature and its Logic  (Richard Dietz & Sebastiano Moruzzi eds., Oxford Press, 2010).
• Vagueness: A Reader  (Rosanna Keefe & Peter Smith eds., MIT Press, 1999)
• Timothy Williamson, <Vagueness (Problems of Philosophy) New Edition by Williamson, Timothy published by Routledge Paperback  (Routledge, 1996)
• Israel Scheffler, Beyond the Letter (Routledge Revivals): A Philosophical Inquiry into Ambiguity, Vagueness and Methaphor in Language  (Routledge, 2010)
• Ralf Poscher, Ambiguity and Vagueness in Legal Interpretation in The Oxford Handbook of Language and Law, Lawrence Solan & Peter Tiersma, eds., Oxford University Press, 2012).
• Scott Soames, Vagueness and the Law in The Routledge Companion to Philosophy of Law (Andrei Marmor ed. 2012).

(This entry was last revised on December 10, 2023.)