The basic idea of Gentner's structure-mapping theory is that an analogy is a mapping of knowledge from one domain (the base) into another (the target) which conveys that a system of relations which holds among the base objects also holds among the target objects. Thus an analogy is a way of noticing relational commonalties independently of the objects in which those relations are embedded. Central to the mapping process is the principle of systematicity: people prefer to map systems of predicates that contain higher-order relations, rather than to map isolated predicates. The systematicity principle is a structural expression of our tacit preference for coherence and deductive power in interpreting analogy. Besides analogy, other kinds of similarity matches can be distinguished in this framework. Whereas analogies disregard object descriptions and map relational structure, appearance matches do the opposite -- they map aspects of object descriptions and disregard relational structure. Literal similarity matches map both relational structure and object-descriptions. As discussed below, these different kinds of similarity play different roles in psychological processes of learning and reasoning.

We view structure-mapping as the mechanism by which much of experiential learning takes place. We conjecture that much of experiential learning is driven by implicit comparisons among a person's knowledge structures at a given time. Analogy is also crucial in learning from instruction and in aligning experiential knowledge with knowledge gained via instruction.