Reasoning by analogy leads to

Concept

An analogical argument notes that two cases resemble each other in several known respects and concludes that they also resemble each other in a further respect. The shared attributes never entail the further attribute, so the step is ampliative: it can make a conclusion more or less likely, but it cannot make it necessary.

Application

The stem asks what such reasoning yields. Because the resemblance between the source case and the target case is partial by construction, whatever is asserted about the target goes beyond the evidence in hand. The output is therefore a forecast held with some degree of probability — a predictive conjecture — whose strength rises with the number, relevance and variety of the shared attributes and falls with every relevant disanalogy.

Cross-check

• certainty and surety describe the epistemic standard of demonstrative proof, where true premises make a false conclusion impossible; an analogy offers no such guarantee, since the observed resemblances leave the inferred attribute logically open.

• a definite conclusion, closed to revision, is the product of deductive forms such as the syllogism or a mathematical derivation; a single relevant disanalogy can defeat an analogical inference, so its conclusion stays revisable.

Hence reasoning by analogy leads to a predictive conjecture.