In Indian logic, which means of knowledge is drawn from the similarity between…

Indian epistemology (pramana-shastra) recognizes several distinct pramanas — independent means by which valid knowledge can be acquired. The classical Nyaya school accepts four: Pratyaksha (direct sensory perception), Anumana (inference through invariable concomitance, vyapti), Upamana (comparison/analogy — knowledge of a thing established through its stated similarity to something already known), and Shabda (verbal testimony of a reliable, trustworthy source).

The question asks which pramana yields knowledge from the similarity between two objects. That description matches Upamana, rendered here as Comparison. Its classic illustration: a person who has never seen a gavaya (wild ox) is told only that a gavaya is like a cow. When that person later perceives an actual gavaya in a forest and recognizes its resemblance to a cow, the new knowledge — this animal is a gavaya — arises purely from the perceived similarity to the already-known cow. That is Upamana in action, so Comparison is the pramana being described.

• Inference draws knowledge from a fixed logical relation between a sign and what it invariably accompanies, such as inferring fire from smoke, rather than from a stated resemblance between two objects.

• Perception is knowledge gained through direct, unmediated contact between the senses and an object, and does not depend on noting a resemblance to another already-known object.

• Implication accounts for an unstated fact that must be assumed true to make two known facts consistent with each other, which is a different process from recognizing similarity between two objects.