Think Again: How to Reason and Argue - Week 3

What makes an argument good? Validity and soundness.

By this standard, a bad argument has:

• Wrong premise, or
• Wrong relation from premises to conclusion (invalid).

Deductive argument is supposed to be valid; inductive argument is not supposed to be valid (we will address this later).

Validity: If all the premises are true, there is no possibility that the conclusion is false (roughly speaking, it means that you can’t find a counter example if all the premises are true). It is unrelated to good or bad; it is purely a technical judgement. So, you might have a valid argument with false premises but true conclusion.

Soundness: A sound argument is a valid argument that both premises and conclusion are true.

Forms of excess verbiage:

• Repetition.
• Road markers.
• Tangents and examples (irrelevant facts and red herring, i.e., distractions).

Clarity: You need just adequate clarity; absolute clarity is not possible in practice. Then how clear is adequate? You have to know your readers. Also, pick the most “charitable” clarity (the clarity that makes the argument looks good).

Structures of an argument:

• Linear: If A then B.
• Branching: If A or B then C (“or” - branching).
• Joint: If A and B then C (“and” - joint).

To reconstruct an argument, you often need to add back suppressed premises.

• Remember the “charitable” principle.
• Don’t add too much or too little suppressed premises.