What is a Categorical Syllogism?

ARISTOTELIAN LOGIC: WHAT THE HECK IS A CATEGORICAL SYLLOGISM? 7/17/10

What in the world is a categorical syllogism? It is “an argument composed of three categorical claims, two premises and a conclusion. The three claims use three terms as subject or predicate, each of which appears in exactly two of the claims.” Got that?? ;o)

The book offers up the following:

No police officers are thieves.
Some thieves are sent to prison.
So no police officers are sent to prison.

The terms “police officers,” “thieves,” “people sent to prison,” appear in two of the claims. Aristotelian logic “identifies the predicates and subjects in syllogisms by the roles they play in determining whether the argument is valid.” For example, major, minor, and middle terms, and major and minor premises. Aristotelians “identify the predicates and subjects in syllogisms by the roles they play in determining whether the argument is valid.” Epstein p. 381.

Epstein states that the major term is: people sent to prison. The minor term is: police officers. The middle term is: thieves. And the major PREMISE is: “Some thieves are sent to prison.” Therefore the minor PREMISE is “No police officers are thieves.”

Aristotelian logic focuses on showing that we can “mechanically determine any given categorical syllogism whether it is valid or invalid. One way to do that is by inspecting its form.” AL lists all forms of syllogisms into STANDARD FORM. The claims are in standard, major premises is first, minor is next, and the conclusion follows. Then you go down each line and determine whether it is valid or invalid.