Rules for Definitions
Avoid Vagueness

This is the clarity rule. The purpose of a definition is to clarify our understanding of a concept. At the very least, therefore, the language we use in a definition should not be less clear than the concept being defined.

A vague definition is unclear because it does not give any precise criterion for membership in the concept. A definition shouldn't have borders that are even fuzzier than those of the concept being defined.

Example:

Suppose we define "maturity" as the stage of psychological development in which a person becomes well-adjusted.

Who belongs in the class of well-adjusted people and who doesn't is unclear; the class has fuzzy boundaries that are even fuzzier than those of the concept being defined.

A Definition Should Avoid Obscurity

An obscure definition is unclear because it uses abstract or technical language that is more difficult to understand than the concept itself.

Example:

Suppose we define "death" as the cessation of one's participation in finitude.

The problem here may not necessarily be one of vagueness. Within a specialized context, this definition might have a perfectly clear and definite meaning. The problem is that if technical definitions are used outside of these specialized contexts they are not clear to the layperson.

A Definition Should Avoid Metaphorical Language

A metaphorical definition is unclear because it doesn't convey the literal meaning of the concept, but only an analogy that we have to interpret.

Example:

Suppose we consider the definition: "Life is a cabaret."

Like any good metaphor, this one uses a simple image to convey a complex thought that would take many paragraphs to explain in literal terms. Metaphorical definitions leave too many questions unanswered, which is why we need literal definitions.


A Genus and a Differentia | Neither Too Broad Nor Too Narrow |
Essential Attributes | Avoid Circularity | Avoid Negative Terms | Avoid Vagueness

Rules for Definitions

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