"Argument evaluation looks at the structure and content of arguments critically. It examines where, why, and how arguments are defective. It also considers ways in which poor arguments may be improved."

- From The Anatomy of Argument, by Barrie A. Wilson, ©1980, University Press of America

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Anatomy of Argument

A Methodology to Assess Deductive Validity and Inductive Strength of an Argument

An argument in this context is a perspective, point-of-view, or opinion: one or more assertions, supported by a collection of premises, which in turn have their own support. An argument can be deductive or inductive, and while an argument can contain heated dialog, that is not the context in which we are speaking.

This method of evaluation can be used as an effective tool to strengthen your own arguments, or to call attention to the weaknnesses in those of your opponents. If your arguments can stand up to this disciplined scrutiny, they should be very difficult to attack.

1. Draw attention to the premises that need support.
2. Look at the language used; is any -
   1. Vague, (no specific meaning),
   2. Ambiguous, (more than one specific meaning),
   3. Using unhelpful language, (to intentionally mislead or confuse),
   4. An undefined, or controversial definition?
3. Are any required premises missing?
4. Look for absent qualifiers, (almost, primarily, usually, always, never, etc.)
5. Are any premises bogus? By:
   1. Ad hominem, (against the person),
      1. Character assassination,
      2. Attacking origins,
      3. Attacking affiliations,
      4. Guilt by association,
   2. Begs the question, (the conclusion is not also a premise),
   3. Appeal to Authority, (even Authoritative assertions need support),
   4. Irrelevant reason,
      1. Appeal to force,
      2. Appeal to pity,
      3. Two wrongs make a right, (because X thinks, believes P, doesn’t mean Y does),
   5. Appeal to ignorance, (because it has not been proven false, does not mean it is true.)
6. Do the premises give sufficient support?
   1. False dilemma, (failure to state all reasonable outcomes),
   2. Slippery slope reasoning, (unsupported cause and effect relationship),
   3. Hasty conclusion, (missing premises.)
7. How does it stand in relation to other arguments?
   1. Misrepresentation of opponents statements and/or position,
   2. Straw Man, (easier to attack than the real issue),
   3. Inconsistency,
      1. Contradiction,
      2. Words changing meaning,
      3. Change in details.
8. If Deductive, Is it valid or not?
   1. By Truth Table, (Boolean logic),
   2. Common Patterns, (see Table 8.2.)
9. If Inductive, - the quality is determined by:
   1. Clear Key Expressions,
   2. Supported premises,
   3. Informative Inductive Base,
   4. Use of Statistics -
      1. Dubious statistics,
      2. Absurdly precise,
      3. Improper comparisons,
      4. Omitted statistics,
      5. Size of Sample,
      6. How well does sample represent norm?

Table 8.2: Common Deductive Patterns

P Q, P Q	Modus Ponens - valid: "IF P is true, THEN Q is true; P is true, therefore Q is true."
P Q, Q, P	Modus Tollens - valid: "IF P is true, THEN Q is true; Q is false, therefore P is false."
P Q, P, Q	Disjunctive syllogism - valid: "Either P OR Q is true; P is false, therefore Q must be true."
P Q, Q R, P R	Hypothetical syllogism - valid: "IF P is true, THEN Q is true; AND IF Q is true, THEN R is true; therefore IF P is true, THEN R is true."
P Q, P Q	Fallacy of denying the antecedent - invalid: "IF P is true, THEN Q is true; P is false, therefore Q is false."
P Q, Q P	Fallacy of affirming the consequent - invalid: "IF P is true, THEN Q is true; Q is true, therefore P is true."

Adapted from "The Anatomy of Argument", by Barrie A. Wilson, ©1980, University Press of America

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