October 24 2012
Definition and Counter-Example
Importance of Definitions:
Definitions are found all over in philosophy, doing much of the important conceptual
work. Here’s three general jobs:
1. Definitions answer many of the basis philosophical questions.
Ex. What is ____? truth? knowledge? reality?
2. In arguments, definitions specify what your premises say about the world
this helps to decide the truth of your premises.
3. In arguments, definitions determine what your conclusion affects
helps decide the relevance of the argument.
Rules for creating / evaluating definitions:
1. Don’t include accidental, non-essential features:
ex. Defining money as “green paper”. (Essential feature = true for all X;
accidental feature = no necessarily true for all X)
you add in things that are coincidental
non-essential (accidental) vs. Essential features
philosophers: believe that there has to be an essential features to
2. Definitions establish logical equivalence: you should be able to substitute the
definition for the term defined without loss of meaning.
Ex. Can replace ‘bachelor’ with ‘unmarried male’.
If you can think of a sentence that involves the term and replace the
content for the term and it works, you have a good definition
3. Definitions can be more or less precise, but the degree of precision should be
suitable to the subject matter.
Though to determine ultimately
4. Definitions should not include the term being defined:
ex. Definition = one expression that defines another.
Circular reasoning, circular definition
ex: sexual desire: desire for certain bodily pleasures
5. Definitions should be neither too broad or too narrow.
Broad: when you look at the field of objects and you discover there are
things people would not count
narrow: criteria that only picks out a subset