Socratic Logic - Judgement

 

The following are the notes I have taken from Peter Kreeft's wonderful Socratic Logic textbook. I highly recommend you buy it. This is a book which deals with classical logic (as opposed to modern symbolic logic.) It is easily the best overall book on logic I have ever read and one of the few I have that are worth making notes from. I even have a small duotang with these notes in it I can carry around and reference on a regular basis.

 

Categorical Propositions

Every proposition has content (matter) and form.  Content can change drastically while form has only two variables: quantity and quality.

 

There are four basic types of Categorical Propositon:

 

I. Universal Affirmative

II. Universal Negative

III. Particular Affirmative

IV. Particular Negative

 

Categorical propositions are at the heart of classical/Aristotelian logic.  Predicate logic (a formal logic) includes this part of classical logic in it.

 

 

A. Universal Affirmative (A)

All men are mortal.

 

B. Universal Negative (E)

No men are mortal.

 

C. Particular Affirmative (I)

Some men are mortal.

 

D. Particular Negative (O)

Some men are not mortal.

 

Singular Propositions

Singular propositions are about not all of a class, or some of a class, but one instance of a class. (An individual)

 

 

Logical Form of Categorical Propositions

 

Translate declarative sentences (ordinary language) into logical form because:

• You can more easily understand what is said.
• You can more easily calculate whether arguments that contain those propositions are valid or invalid.

 

A: All [S] is [P].

E: No [S] is [P].

I: Some [S] is [P].

O: Some [S] is not [P].

 

Quantity: all, no or some.

Quality: is or is not / are or are not

 

 

 

 

 

 

 

 

 

 

 

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