Emergence is, broadly speaking, the fact that there are features of the world—objects, properties, laws, perhaps other things—that are manifested as a result of the existence of other, usually more basic, entities but that cannot be completely reduced to those other entities. Theories of emergence tend to fall into two basic types: ontological emergence and epistemological emergence—with conceptual emergence serving as a subcategory of the latter. Advocates of ontological emergence consider emergent phenomena to be objective features of the world, their emergent status being independent of human existence and knowledge; advocates of epistemological emergence consider emergent features to be a result of the limited abilities of people to predict, to calculate, to observe, and to explain; and advocates of conceptual emergence consider emergent features to be a product of theoretical and linguistic representations of the world.

Emergence has considerable philosophical importance because the existence of...