1.3 Understanding Reasoning: Different Patterns of Reasoning

A. Deduction — reasoning from the general From true premises, a valid deductive argument guarantees its conclusion. Test: if the premises were true, could the conclusion be false? If not — valid.• Valid form (the lawyer's syllogism):P1: Whoever intentionally kills another commits murder (major premise — the rule). P2: A intentionally killed B (minor premise — the fact). C: A committed murder. This is exactly the judicial syllogism — rule + fact = holding (Legal Method's IRAC is its industrial form).• Validity vs soundness: valid = the form holds; sound = valid and premises actually true. A perfectly valid argument from a false premise proves nothing — the daily lesson of appellate litigation.• Formal fallacies (Unit 3.2's full treatment): affirming the consequent, denying the antecedent — seductive invalid forms.B. Induction — reasoning to the general From observed cases to a probable general claim (or from a sample to a population). Never certain — only more or less strong.• Inductive generalisation — 40 of 50 audited firms filed false VAT bills → the practice is likely widespread. Strength depends on sample size and representativeness (the classic exam points).• Causal induction — from correlation to cause (Unit 3.4's cautions: correlation ≠ causation).• Argument from analogy — this case is like that decided case in material respects; it shouldbe decided alike. Analogy is…