I’m working on my first draft of Key Terms in Philosophy of Mind, a book under contract with Continuum Books. From time to time I’ll be posting draft entries on Brain Hammer, especially for controversial or especially difficult to arrive at definitions. Here’s “emergence”:
emergence, the arising of a property in a relatively unpredictable way from the interaction of other properties. Alternately, the instantiation of a property by a whole that is due to “more than the sum of its parts”, or, less colloquially, due to properties of the parts in a way more complicated than mere summing. Part of what’s difficult in supplying a viable notion of emergence is the task of characterizing a relevant notion of unpredictability that isn’t due simply to the current ignorance of investigators. Early proponents of the existence of emergent properties claimed that certain chemical properties like the liquidity or solubility of certain chemical samples were emergent on the grounds that they could not be predicted by knowledge of the nature and interaction of their atomic constituents. However, as chemistry and physics progressed, such claims were discovered to be false. Another difficulty in supplying a viable notion of emergence is in giving a precise meaning to the imprecise phrase “more than the sum of its parts”. We can see that there are clear cases in which the property of a whole is more than a sum of properties of its parts but that the properties of the whole are unlikely to be regarded by anyone as having emerged from the properties of the parts. For example, the temperature of a gas is the average kinetic energy of its constituent molecules. As such, it is thus not simply the sum of the molecule’s kinetic energy. It is instead the sum of their kinetic energy divided by the number of molecules. There’s a sense in which being a divided sum of its parts is more than the sum of its parts: since it involves division, it involves a further arithmetical operation than mere summing. However, this seems not to get at the sort of thing that emergentists have had in mind, perhaps since the result of the operation is insufficiently surprising or unpredictable. Emergentism, the proposal that there exist emergent properties, is closely related to non-reductive physicalism (see PHYSICALISM, NON-REDUCTIVE).