Logic and Scientific Method
Logic and Scientific Method tests formal validity, inductive strength and the difference between discovery and justification. You must use standard terminology and spot fallacies.
Core rules
- Inference: deductive arguments aim at validity-if premises are true, the conclusion cannot be false. Inductive arguments aim at strength-premises make the conclusion probable.
- Categorical syllogism: three terms (major, minor, middle), three propositions (major, minor, conclusion); figure determined by middle-term position. Mood and figure determine validity; Venn diagrams test it.
- Soundness = validity + true premises.
- Induction: enumeration, analogy, causal inference. Mill's methods: agreement, difference, concomitant variation, residues, joint method.
- Scientific method: hypothesis, operational definition, prediction, experiment, confirmation/falsification, theory. Correlation is not causation.
- Fallacies: affirming the consequent, denying the antecedent, petitio principii, post hoc, hasty generalization.
Worked example
‘All mammals are warm-blooded; all whales are mammals; therefore all whales are warm-blooded.’ This is AAA-1 (Barbara), valid: the middle term ‘mammals’ is distributed in the major premise and the conclusion's predicate is distributed in the major. It is sound only if both premises are true.
Traps
Do not call a valid argument true; validity concerns form. Do not confuse Mill's method of difference with agreement. Do not treat a hypothesis as confirmed by one positive instance. Do not use ‘proof’ for inductive support.