Analogy and Scientific Method
Analogy argues from similarity, while scientific method systematises observation, hypothesis and testing. The exam tests analogical form, criteria of strong analogy, Mill's methods and the logic of confirmation and falsification.
Core rules
- Analogy: A and B share properties p, q and r; A has feature x; therefore B probably has x. Strength depends on relevant similarities, number of similarities and absence of relevant disanalogies.
- Scientific method typically moves from observation and problem to hypothesis, prediction, experiment and confirmation, revision or rejection.
- Mill's methods include agreement, difference, concomitant variation and residues. Method of difference is especially strong for causal inference.
- A good hypothesis must be testable and falsifiable; confirmation is not proof.
Worked example
Two plots have the same soil, water and light; only one receives fertiliser. The fertilised plot grows taller. By the method of difference, the fertiliser is inferred as the cause of the difference, because the other relevant factors are held constant. If the plots also differed in light, the inference would be weak because a disanalogy would remain.
Traps
A weak analogy rests on irrelevant similarities. Do not treat post hoc succession as causation. Do not confuse confirmation with conclusive proof. In Mill's method of agreement, look for the one common factor across cases; in difference, hold other factors constant.