Validity and Soundness

Virtues in arguments:

1. Validity
2. Soundness

Relation between premises and conclusion

In a deductive argument, the conclusion should follow from the premises

A deductive argument is supposed to be valid. An Inductive argument is not supposed to be valid.

Validity

An argument is Valid if and only if

It is not possible that both all of its premises are true and its conclusion is false

An argument with a false premise can still be valid.

Soundness

In a Sound argument, the conclusion must be true.

An argument is Sound if and only if

1. all of its premises are true, and
2. it is valid

If a deductive argument is not sound, then it is not a good argument.

Argument Reconstruction

Stage I: Close Analysis

Stage II: GET Down to basics

1. Remove all excess verbiage
2. List all explicit premises and conclusion in standard form

Stage III: Sharpen Edges

1. Clarify where needed
2. Break up where possible without distortion

Stage IV: Organize parts

1. Divide the argument into sub-arguments, and arrange them in order

Stage V: Fill in gaps

1. Assess whether each argument is valid
2. Add suppressed premises where needed
3. Check each premise for truth
4. Qualify premises to make them true where needed if possible

Stage VI: Assess the argument

1. Conclude

Stage II: Get Down to basics

Remove all excess verbiage

1. Repetition
2. Road Markers are helpful for keeping track of an argument, but they do not add anything to the argument itself.
3. Tangents (离题的)
4. Examples

The trick of excess verbiage

The trick of excess verbiage is to hide a problem with an argument by saying too much.

Stage IV: Organize parts

1. Linear structure: One argument depends on another argument linearly
2. Branching structure: Multiple premises support one argument
3. Joint structure: two premises working together (&)

Stage V: Fill in gaps

1. Assess whether each argument is valid
2. Add suppressed premises where needed
3. Check each premise for truth
4. Qualify premises to make them true where needed if possible

Goals of filling in suppressed premises

1. To trace the full path of the arguer’s reasoning (Reason is to understand the pathway between the premises and conclusion, we want to understand how the reasoning works step by step)
2. To find out if there are any missteps in the argument

Types of suppressed premises

1. Factual