Conversely, an added condition may be too narrow and exclude genuine members of the species. Such an account fails to cover all the intended instances.
For example, defining a human as “a rational animal who can write” is defective: many humans cannot write, yet remain human.
A definition must not import a restriction that is not necessary for membership in the target kind. It should express the essence or appropriate identifying feature, not an incidental qualification.
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Definition and Its Four Forms: Complete/Incomplete Essential and Descriptive Definitions
Conversely, an added condition may be too narrow and exclude genuine members of the species. Such an account fails to cover all the intended instances.
For example, defining a human as “a rational animal who can write” is defective: many humans cannot write, yet remain human.
A definition must not import a restriction that is not necessary for membership in the target kind. It should express the essence or appropriate identifying feature, not an incidental qualification.