Lawmaking is – paradigmatically – a type of speech act: people make law by saying things. It is natural to think, therefore, that the content of the law is determined by what lawmakers communicate. However, what they communicate is sometimes vague and, even when it is clear, the content itself is sometimes vague.

This monograph examines the nature and consequences of these two linguistic sources of indeterminacy in the law. The aim is to give plausible answers to three related questions: In virtue of what is the law vague? What might be good about vague law? How should courts resolve cases of vagueness? It argues that vagueness in the law is sometimes a good thing, although its value should not be overestimated.

It also proposes a strategy for resolving borderline cases, arguing that textualism and intentionalism – two leading theories of legal interpretation – often complement rather than compete with each other.

1. Authority, Communication and Legal Content
I. The Communicative-Content Theory of Law and Its (Recent) Critics
II. The Pro Tanto View about Legal Content
III. Authority, Communication and Legal Content
2. On the Instrumental Value of Vagueness in the Law
I. Incommensurate Multidimensionality, Extravagant Vagueness and Endicott's Argument from Instrumental Necessity
II. Incommensurate Multidimensionality is Doing the Real Work
III. The Impossibility of Specification
IV. Are Incommensurate Multidimensionality and – Hence – Vagueness Really Necessary?
V. Waldron's Argument from Facilitation
VI. Possible Reply: Vagueness Really is a Means to the Relevant Ends
VII. Another Possible Reply: The Logic of Value Validates Closure under Necessary Consequence
3. Vagueness and Power Delegation in Law
I. Sorensen's View
II. The Value of Vagueness
III. Summary
4. Vagueness, Uncertainty and Behaviour
I. Endicott's Argument from Comparative Value
II. Hadfield on the Value of Vagueness-related Uncertainty
III. Sorensen on Vagueness-related Uncertainty and Legal Unpredictability
5. On the Possibility of Non-literal Legislative Speech
I. The Conditions for Non-literal Speech and the Legislative Context
II. Revising the Argument: Restrict, Reconstruct, or Both?
III. Testing the Argument against Experience: Ekins's Argument from Examples
IV. Indeterminacy about Utterance Content
6. Textualism, Content and Interpretation
I. Textualism and Legislative Intentions
II. Textualism, Communicative Content and Legal Content
III. Textualism/Originalism and Contextual Enrichment
IV. On the Plausibility of Conception Textualism
V. Contemporary Textualism and the Problem of Legislative Context
VI. Textualism and Legal Interpretation
7. Resolving Cases of Vagueness
I. Expressly Offered Rationale and the Notion of Commitment
II. Institutional Remedies to Non-co-operation
III. Is Expression Required?
IV. Commitment and Counterfactuals
V. Legislative Rationale and Levels of Abstraction
VI. Authority, Legislative Bargaining and Maximising Fidelity to Law
VII. Expressly Acknowledged Compromise vs Tacitly Acknowledged Compromise
VIII. Conclusion
8. Legal Practice and Theories of Vagueness
I. Explaining the Value of Vagueness in the Law
II. A Closer Look at Soames's Argument
III. Generalising the Argument: Other Cautionary Tales