1. Demonstrative (Ostensive) Definitions

An extensional definition assigns meaning to a term by indicating the members of the class that the term denotes. One type of extensional definition is a demonstrative definition, also called an ostensive definition. A demonstrative definition assigns meaning to a word by pointing or gesturing at the thing(s) the word refers to. There are also two types of demonstrative definitions. In a partial demonstrative definition, only some members of the class denoted by the term being defined are pointed to. In a complete demonstrative definition, every member of the class denoted by the term being defined is pointed to.

Demonstrative definitions can be very effective, but they can also be limited because of the possibility that the observer may misconstrue the essential meaning of a term. For instance, if you attempt to define "table" by pointing to a wooden table, the observer may mistakenly gather that the word "table" means "made of wood." In addition, demonstrative definitions are limited because they require the presence of something at which to point or gesture.

Consider each of the following hypothetical cases. In each case a person is using either a partial demonstrative definition, a complete demonstrative definition, or a different extensional definitional technique. For each case, indicate which of these three options is exemplified.

Definition A

AMBER: "Marble" means these (while pointing to a bag of marbles in a toy store).

The definition offered by Amber is definition.

Definition B

LYNN: "Actress" means a person such as Alyson Hannigan, Scarlett Johansson, Renee Zellweger, Meg Ryan, or Anna Paquin.

The definition offered by Lynn is definition.

Definition C

AUSTIN: "Hope Diamond" means this jewel (while pointing to it).

The definition offered by Austin is definition.

Definition D

ROGER: "Airplane" means a 747, B-24, P-51, F-14, Stearman, and the like.

The definition offered by Roger is definition.

2. Enumerative Definitions

An extensional definition assigns meaning to a term by indicating the members of the class that the term denotes. An enumerative definition is a type of extensional definition that assigns meaning to a term by naming the individual members of a class that the term denotes. A partial enumerative definition names a finite subset of members from the whole class that a term denotes. By contrast, a complete enumerative definition individually names every member of the class denoted by a term. Unlike a demonstrative definition, an enumerative definition only involves naming the individual objects denoted by a term rather than indicating them by gesturing or pointing. You should note that an enumerative definition does not name subclasses of objects, but instead names the individual objects or class members themselves.

Indicate whether each of the following definitions is a partial enumerative definition, is a complete enumerative definition, or is not an enumerative definition.

Definition A

"Branch of the United States armed forces" means the U.S. Army, U.S. Marine Corps, U.S. Navy, U.S. Air Force, or U.S. Coast Guard.

Definition A is definition.

Definition B

"Former president of the United States" means a person such as Martin Van Buren, James Polk, Millard Fillmore, Franklin Pierce, or Chester Arthur.

Definition B is definition.

Definition C

"Orchestral instrument" means an instrument such as an oboe, a flute, a violin, or a timpani.

Definition C is definition.

Definition D

"Scientist" means a person such as Albert Einstein, Louis Pasteur, or Stephen Hawking.

Definition D is definition.

3. Definition by Subclass

An extensional definition assigns meaning to a term by indicating the members of the class that the term denotes. A definition by subclass is a type of extensional definition that assigns meaning to a term by naming subclasses of the class that the term denotes. A definition by subclass is complete if the subclasses named, when taken together, include all members of the class that the definiendum denotes. A definition by subclass is partial if the subclasses mentioned, when taken together, do not include all members of the class that the definiendum denotes. The things named in a definition by subclass are smaller classes of the items within the larger class; they are not the individual members of the larger class themselves. This is what differentiates a definition by subclass from an enumerative definition.

Indicate whether each of the following definitions is a complete definition by subclass, is a partial definition by subclass, or is not a definition by subclass.

Definition A

"Navy ship" means an aircraft carrier, a cruiser, a frigate, and the like.

Definition A is definition by subclass.

Definition B

"Ship" means a vessel such as the USS Enterprise, USS John F. Kennedy, or the USS Constitution.

Definition B is definition by subclass.

Definition C

"Matter" means either a solid, a liquid, a gas, or a plasma.

Definition C is definition by subclass.

Definition D

"Mammal" means something such as a dolphin, a hamster, an otter, a fox, or a cheetah.

Definition D is definition by subclass.

4. Applicability of Extensional Definitions

Use your knowledge of specific extensional definitional techniques, and of the distinction between extensional (denotative) definitions and intensional (connotative) definitions, to answer the following questions.

What is one reason that extensional definitions cannot adequately serve as precising definitions?

Vagueness of a word is a problem affecting extensional meaning, not intensional meaning.

The correct relationship between intension and extension is that extension determines intension.

Since vagueness is a problem affecting intensional meaning, the extension of a vague term is not precisely defined.

Since a precising definition has a definiendum that is already precisely defined without vagueness, there is no need to give a list of the term's extension.

Which extensional definitional technique assigns meaning to a term by naming members of the class denoted by the term being defined?

Enumerative definition

Operational definition

Intensional (connotative) definition

Definition by subclass

Definition by genus and difference

What are the two broad categories that individual definitional techniques fall under? Check all that apply.

Intensional (connotative) definitions

Enumerative definitions

Demonstrative definitions

Extensional (denotative) definitions

Definitions by subclass