Classical Logic - Introduction

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.

Two types of reasoning:

a) Deductive - when correct, yields certainty

b) Inductive - yields probability, not certainty

Three Conditions for a Deductive Argument to be True:

a) all terms must be clear and unambiguous

b) all premises must be true

c) the argument must be logically valid

Acts of the Mind

Three Acts of the Mind:

a) simple apprehension

b) judging

c) reasoning

Three Mental Products (Produced by Above Acts of Mind):

a ) concepts (products of conceiving)

b) judgments (products of judging)

c) arguments (products of reasoning)

Three Mental Entities Expressed in Logic:

a) terms

b) propositions

c) arguments

 

Three Equivilents of Above in Language

a) words or phrases

b) declarative sentences

c) paragraphs (2 or more declarative sentences, plus an indicator word like therefore.)

Structural Parts of Logical Entities:

a) terms - none

b) propositions - subject term + predicate term

c) argument - premises and conclusion

Questions Logical Entities Answer:

a) terms - what it is

b) propositions - whether it is

c) arguments - why it is

Aspects of Reality Three Entities Reveal:

a) terms - essences

b) propositions - existences

c) arguments - causes

How to Judge the Correctness of the Entities:

a) terms - are they clear or unclear

b) propositions - are they true or false

c) arguments - are they valid or invalid

Most Important Questions to Ask in Logic

1 . What do you mean? (Define your terms)

2.  What is your point? (What is your conclusion?)

3.  Why? (Prove it!)

So:

1. Your terms should be clear.

2. Your premises should be true.

3. Your argument should be valid.