“We’re in the 4th Grade.  We don’t even know what ‘ethical’ means.” - Cartman


A definition is a statement that specifies the proper application of a term or concept.

The defined concept is sometimes called the definiendum (that which is defined), while the rest of the definition is called the definiens (that which does the defining).


Rules for evaluating and constructing definitions:

1) No Counterexamples – Ideally, a definition provides both necessary and sufficient conditions for applying a term: 

If a definition’s definiens fails to include stuff that it should, then it doesn’t provide appropriate necessary conditions; in this case, it is too narrow.

If a definition’s definiens includes stuff that it should not, then it fails to provide appropriate sufficient conditions; in this case, it is too broad.

 Here’s an example.  Consider the following proposed definition:

A bird is an animal that flies

In this definition, the definendum is ‘bird,’ while the definiens is ‘animal that flies.’

However, the definiens is too narrow.  Penguins are birds, yet they aren’t flying animals.  Thus, being a flying animal isn’t a necessary condition for being a bird.

This definiens is also too broad.  Bats are flying animals, but they aren’t birds.  So being a flying animal is not a sufficient condition for being a bird.

By the way, this example illustrates something that might at first seem counterintuitive.  A definition’s definiens can be both too broad and too narrow at the same time

2) Proper Form: Ideally, a definition’s definiens will include both a genus and a differentia (lists of examples do not exhibit proper form!)

Genus: The broader class to which a defined concept belongs

Differentia: The features that set the defined concept apart from other members of its genus.


 3) Even if a definition has no counterexamples, a definition might nevertheless fail to focus on just the right characteristic that makes something belong to a certain concept.  That is, definitions need to be based upon Essential Characteristics

 4) Definitions ought to avoid metaphor and obscurity.

 5) Definitions ought to avoid circularity (placing the defined concept or one of its cognates in the definition).

 6) Finally, we ought (as much as possible) to avoid negative definitions (those that attempt to define a concept by specifying what the defined concept is not).




Identify the definiens and definiendum of each of the following proposed definitions.  Then pick out the rule-violations in the following definitions. Try to construct better ones.

1. An army is the branch of a country’s military that uses tanks.

2. A genus is the generic class to which the referent of a given concept belongs.

3. Beer is pure goodness.

4.  Beef – it’s what’s for dinner!

5.  Orange is an autumn hue that isn’t brown.

6. Psychology is the science that studies human behavior.

7. A mullet is business in the front, party in the back!

8.  El Camino, El, El Camino – In the front it’s a car, in the back it’s a truck….(chant)

9.  Oh, so you mean that an El Camino is the mullet of the car world!

10. A definition is the enclosing a wilderness of ideas within a wall of words.

11.  “Philosophy is the study of the normative in all its guises.” – R. Brandom, Reason in Philosophy

12.  Ethics is all about not getting punished.

13.  Love is … what I got.

14.  “Love is never having to say you’re sorry.” – Love Story

15.  Bottommost (adj): 1. sited at the very bottom.  2. Being or coming after all others.  Last.  3. UNLV’s predicted finish in Mountain West Conference football (Rebel Yell, July 25, 2005)

16.  A living thing is any semi-closed physical system that exploits order it already possesses, and the energy flux through it, in such a way as to maintain and or increase its internal order.