Vices in arguments

• Premises are false.
• The premise does not provide good reason for conclusion.

Virtues in arguments

• Validity
• Soundness

Deductive arguments

• The conclusion should follow from the premise.
• Is trying to be valid.

An argument is valid if and only if it is not possible that all the premises are true and conclusion is false.

Valid Arguments

• Not all premises need to be true.
• Validity is technical term and valid argument is not necessarily a good argument.
• Not based on what is true, but what can be true when determining validity of an argument.
• Validity is a necessary condition not sufficient.

An argument is sound if and only if all of its premises are true and it is valid.

Soundness

• Conclusion has to be true.
• Arguments can be valid but not sound.

Argument Reconstruction

Goal of reconstruction is to make it easier to assess whether argument is good or bad.

Stages of Reconstruction

• Stage 1. - Close analysis.
• Stage 2. - Get down to basic
  • Remove all excess content.
    • Repetitions, road markers, tangents, red herring, examples.
    • Make sure that you have not removed any essential content.
    • Guarding and assuring terms can sometimes be removed.
  • List all explicity premises and conclusions in standard form.
• Stage 3. - Sharpen the edges.
  • Get explanation for things which are unclear.
  • Break up premises where possible.
• Stage 4. - Organize
  • Divide in subparts and put them in correct order.
  • Linear, joint, or branch structures or a combination thereof.
• Stage 5. - Fill in the gaps
  • Assess whether each argument is valid.
  • Add missing premises where needed.
  • Check each premise for truth.
• Stage 6. - Assess the argument.