ABSTRACT
The concept of emergence has a twofold meaning: the fi rst ontological and the second epistemic. (1) In the ontological domain, a system is said to be emergent with respect to the subsystems of which it is constituted when the laws that govern its structure (including the laws of development that characterize it) cannot be derived from the laws of its subsystems. An emergent system is therefore endowed with an essentially irreducible structure, and description of this structure is assigned to an ontological theory irreducible to the ontological theory able to describe the subsystems of the system in question. (2) In the epistemic domain, the concept is applied to the evidence systems at the basis of justifi cation of particular theories: an evidence system is said to be emergent with respect to other evidence systems when the theories justifi able on the basis of the fi rst system are irreducible to the theories justifi able on the basis of the other systems considered. An emergent evidence system is therefore one which gives access to information that is essentially new with respect to the information yielded by the systems from which it is emergent. Consequently, theories based on this information are irreducible to theories based on information of another type. The two concepts of emergence are linked by the fact that systems of evidence which are such to allow access to emergent structures are epistemically emergent with respect to those necessary to access less complex ontological systems.
