Emergence is the idea that qualitative changes in a system may occur which have characteristics not anticipated by preceding states. Bunge ( 1977) has argued that emergence is a characteristic of the aggregate of a system; otherwise, each component would be required to have the properties of the whole. In principle, emergence could be accounted for by interaction among the components of a system. The question, then, is what is the emergent property that is explained in this way?
In evolution, the idea of emergence has been resisted by those who consider it a metaphor for entelechy or élan vital. The problem is that the emergent step does not lend itself to analysis. Can an emergent system have causal properties? Presumably, if we knew all there was to know of a particular state, what appears as an emergent from this state could be explained or predicted on a quantitative basis. For example, when ice melts to water and then vaporizes to steam, each appears as a different qualia but occurs on a continuum of physical change. Are emergents really "resultants" awaiting physical explication? In evolutionary theory the question of emergence is difficult to assess. It is not even clear what would be required to confirm or disconfirm the idea.
In some instances, emergence refers to the appearance of a behavioral (mind) state out of a physiological (brain) state -- that is, to the mind-body problem. Or, emergence is used to describe successive levels in a systems organization, e.g., molecular → biological → mental → social. In neuropsychology, emergence can be applied to the problem of part: whole relationships. Partial functions may coalesce in a manner to suggest emergent phenomena. This was the view of the Gestalt theorists, and it has recently been advocated by Sperry ( 1976). Of course, it is not clear how the effect occurs. One interpretation is that the frequencies of different oscillators (cells, machines) are mutually entrained, or synchronized, by virtue of their belonging to a single interconnected group. There is certainly good reason to believe that oscillatory systems play an important role in speech and motor function ( Brown, 1982).____________________