10-11-2012, 04:51 PM
Critical Thinking:A User’s Manual
Critical Thinking.ppt (Size: 423.5 KB / Downloads: 280)
EvaluatingTruth-Functional Arguments
Truth-functional arguments may be valid or invalid.
Demonstrate by identifying argument forms.
Demonstrate using Truth Table Method.
Demonstrate using Shortcut Method.
Invalid Argument Forms
Y is a necessary condition for X.
Y is true.
Yet, we cannot conclude that X is true; Y is necessary, not sufficient for X.
Truth-Functional Definitions
A truth-functional definition specifies when a compound claim is true and when it is false.
Used to complete Truth Tables
Using the Truth Table Method
Step 1: Translate the argument into symbolic form.
Step 2: Write the argument horizontally, using / to separate premises and // in front of the conclusion.
Step 3: Calculate the number of lines in the truth table using the formula, L = 2n.