For my last discussion question of the week, I'm going to focus on valid and weak forms of arguments using conditionals. There are several different reasoning structures that the book contains that help in creating and evaluating arguments with conditionals.
In terms of valid arguments, there are the reasoning structures of:
Direct Reasoning: Indirect Reasoning:
If A, then B If A, then B
A Not B
So B So not A
These formats are pretty easy to understand. When looking at an argument, assign the appropriate "A" and "B" labels to the argument and check what format it follows.
Here's a Direct Reasoning example:
(A) If it's raining outside, (B)Johnny will wear a jacket
(A) It's raining outside
(B) So Johnny will wear a jacket
Weak arguments generally follow this format:
Affirming the Consequent: Denying the Antecedent:
If A, then B If A, then B
B Not A
So A So not B
These formats usually are associated with weak arguments because they often resort to "arguing backwards". These formats are similar to the Direct/Indirect way of reasoning with conditionals, but the minute differences make all the difference.
Here's an Affirming the Consequent example:
(A) If it's raining outside, (B) Johnny will wear a jacket
(B) Johnny wore a jacket
(A) So it's raining outside
Instead of proving the "then" part of an "if, then" conditional, weak arguments usually resort to proving the (A) part of the argument as in the example. It's very easy to get these concepts confused, but once you get the formats down for each associated reasoning structure, you'll be perfect at evaluating and writing arguments using conditionals.
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