The Purpose of Definition

To explain a theory. A definition may carry a whole account of what a thing is: the definition of "negligence" as breach of a duty of care carries a theory of when liability arises.

To influence attitude. A definition may be framed to make its subject attractive or repellent, and it is then a persuasive definition. "Taxation is legalised theft" is a definition doing rhetorical work, and it is worth being able to name what is happening.

Why the purpose has to come first

Because a definition cannot be assessed without one. A definition of "vehicle" that includes a bicycle is right for a road safety Act and wrong for a motor insurance Act, and nothing about the word settles which. The question is never "is this the correct definition" but "is this the right definition for this purpose".

Because the rules of definition apply differently by purpose. The rule against circularity applies to every kind. The rule that a definition must not be too wide or too narrow applies to a lexical definition, which reports usage and can be wrong about it; it does not apply in the same way to a stipulative definition, which creates a usage and cannot be wrong about it, though it can be useless.

And because it explains why one word has many definitions. The same word is defined differently in twenty statutes, and none of them is a mistake. Each is a précising definition made for its own Act, and asking which is the true meaning of the word is asking a question that has no answer.

A worked example

Take the word "employee".

In an Act about provident fund contributions, the purpose is to fix who must be covered by a savings scheme, and the definition will be drawn widely, taking in casual and contract workers, because leaving them out would defeat the object.

In an Act about industrial disputes, the purpose is to fix who may raise a dispute and be represented, and the definition will exclude those in a managerial or supervisory capacity above a stated pay, because the scheme is built on a distinction between labour and management.

In the law of vicarious liability, the purpose is to fix when one person answers for the wrong of another, and the test developed by the courts asks about control, integration and the nature of the engagement, because what matters is who was directing the work.

In an internal company policy, the purpose may be to decide who gets a canteen pass.

Four definitions of one word, none of them wrong. A student who asks which is the real meaning of "employee" has not understood what a definition is for. What can be asked, and is asked in litigation every day, is whether the definition in this instrument covers this person, and that question is answered from the instrument's own words and its own purpose.

Distinctions that carry marks

What this does not mean

A definition is not a description of a thing. It is a statement about a term, and it is tested against uses of the term and not against samples of the thing.

There is no single true definition of a word. There is a correct report of usage, which a lexical definition attempts, and there are useful definitions for particular purposes, which everything else attempts.

A definition is not an argument. It asserts nothing about the world, so it cannot be a premise from which facts follow. What it does is fix what the other premises mean, which is why an argument that turns on a shifting definition commits the fallacy of equivocation at sequence 160.

Quick revision

Definiendum is the term defined; definiens is what defines it.

A definition is about the term, not about the thing, and it states a connotation, which fixes a denotation.

Six purposes: fix an unsettled meaning; settle a verbal dispute; reduce vagueness for a purpose; introduce a new term; explain a theory; influence attitude.

A definition is judged against its purpose. There is no question whether a definition is correct in the abstract.

One word, many definitions, each made for its own instrument, and none of them the true one.

A definition is not an argument and establishes no facts.

Test yourself

1. What is a definition, and what are its two parts called?

A definition is a statement of the meaning of a term. Its two parts are the definiendum, the term being defined, and the definiens, the words offered as its meaning. In "a contract is an agreement enforceable by law", the definiendum is "a contract" and the definiens is "an agreement enforceable by law", and the rules of definition all govern the relation between the two.

2. Name the purposes a definition may serve.

To fix a meaning where usage is unsettled; to settle a verbal dispute by showing that a disagreement is about a word rather than about the facts; to reduce vagueness by drawing a sharp line for a particular purpose; to introduce a new term or give an old one a new sense; to explain a theory, the definition carrying an account of the thing; and to influence attitude, which is what a persuasive definition does.

3. Why must the purpose be settled before a definition can be assessed?

Because a definition is good or bad only in relation to a purpose. A definition of "vehicle" that includes a bicycle is right for a road safety statute and wrong for a motor insurance one, and nothing about the word itself decides which. The question is never whether a definition is correct in the abstract, but whether it is the right definition for the use to which it is being put.

4. Why is a definition said to be about the term and not about the thing?

Because it states what a word means rather than describing an object, and it is tested accordingly: a definition is not refuted by producing a sample of the thing but by producing a use of the word that the definition fails to cover or wrongly covers. This also explains why a definition asserts nothing about the world and cannot serve as a premise from which facts follow.

5. How can one word have four different statutory definitions without any of them being wrong?

Because each is a précising definition made for its own instrument and its own purpose. "Employee" is drawn widely in a provident fund statute so that the savings scheme covers those it was meant to cover, and more narrowly in an industrial disputes statute so that the scheme's distinction between labour and management works. Asking which is the real meaning of the word is asking a question that has no answer; the real question is whether this instrument's definition covers this person.

6. What is a verbal dispute, and how does a definition end it?

A dispute in which the parties agree about all the facts and still disagree, because they are using a word in different senses. One says the meeting was properly convened because notice was sent, the other that it was not because nobody received it; nothing is in issue but the meaning of "convened". A definition ends it by fixing the sense, after which either the disagreement disappears or it turns out to be a real disagreement about the facts or about what the rule should be.