Socratic Logic - Reasoning

Dilemmas

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.

Common in everyday use, dilemmas are a combination of logic and rhetoric.  A dilemma is a syllogism with a disjunctive (either/or) premise and two hypothetical (if-then) premises, one for each of the two premises.  The disjunctive premise sets up the horns of the dilemma.

Four Types of Dilemmas

A. Simple constructive dilemma - conclusion is categorical and affirmative

B. Simple destructive dilemma - conclusion is categorical and negative

C. Complex constructive dilemma - conclusion is disjunctive and affirmative

D. Complex destructive dilemma - conclusion is disjunctive and negative

How to Construct A Dilemma

A. Formulate the conclusion you want to prove.

B. Find an appropriate middle term to connect the subject and predicate of your conclusion.  Should be mutually exclusive, x or non-x.

C. Formulate the two premises.

1. The two horns of your dilemma, hypothetical premise. (if-then premises)

2. The disjunctive (either-or) premise forces the reader to choose between the two horns.

Three Ways to Answer A Dilemma

Very rarely do dilemmas contain a formal fallacy.

A. Check for ambiguous terms.

B. If there are no ambiguous terms, you might need to deny one of the premises.

1. Denying the hypothetical premise is called "taking it by the horns".

2. Denying the disjunctive premise is called "escaping between the horns".

C. You could also construct a counter dilemma called a rebuttal that proves the opposite conclusion.