In philosophy, emergentism is the belief in emergence, particularly as it involves consciousness and the philosophy of mind, and as it contrasts (or not) with reductionism. A property of a system is said to be emergent if it is more than the sum of the properties of the system‘s parts.
Physicalism may be defined as the theory that the universe is comprised exclusively of physical entities. However, consciousness, for example, appears to be problematic for this thesis, as it exhibits properties not ordinarily associated with most other physical entities. In response to this situation, two variants of physicalism have been advanced: reductionism and emergentism.
Reductionists generally see the task of accounting for the possibly atypical properties of mind and of living things as a matter of showing that, contrary to appearances, such properties are indeed fully accountable in terms of the properties of the basic particles of nature (or in other, like terms), and therefore in no way genuinely atypical. By contrast, emergentists have argued that what is meant by the physical is more complex than this picture suggests, and that novel properties can arise above the level of fundamental particles. Thus, emergentism suggests a layered view of nature, with the layers arranged in terms of increasing complexity with each requiring its own special science.
Some philosophers hold that emergent properties causally interact with more fundamental levels, while others maintain that higher-order properties simply supervene over lower levels without direct causal interaction. The latter group therefore holds a definition of emergentism which can be stated as follows:
- a property P of composite object O is emergent if it is metaphysically possible for another object to lack property P even if that object is composed of parts with intrinsic properties identical to those in O and has those parts in an identical configuration.
This purely metaphysical account, by no means the only one possible, and certainly not the most plausible, would seem to lack physical examples.
C. D. Broad provided an entirely different definition:
Put in abstract terms the emergent theory asserts that there are certain wholes, composed (say) of constituents A, B, and C in a relation R to each other; that all wholes composed of constituents of the same kind as A, B, and C in relations of the same kind as R have certain characteristic properties; that A, B, and C are capable of occurring in other kinds of complex where the relation is not of the same kind as R; and that the characteristic properties of the whole R(A, B, C) cannot, even in theory, be deduced from the most complete knowledge of the properties of A, B, and C in isolation or in other wholes which are not of the form R(A, B, C).
The first emergentist theorists used the example of water having a new property when hydrogen, H, and oxygen, O, combine to form H2O (water). In this example there emerge such new properties as liquidity under standard conditions. (Analogous hydrides of the oxygen family, such as hydrogen sulfide, are gases). However, a better and more recent example of an emergent phenomenon, one provided by physicist Erwin Schrödinger, is found in the case of families of molecules known as isomers, which are made up of precisely the same atoms, differently arranged, which nevertheless have different physical properties. Similarly, enantiomers are molecules made up of precisely the same atoms, in precisely the same arrangement, but which exist in “right-handed” and “left-handed” forms, and also have different properties when interacting with other molecules.
Biologists Ursula Goodenough and Terrence Deacon in their 2006 essay on emergencehave assembled a range of examples of physical and biological emergent properties that provide the evidential basis for emergentism as a philosophy that comports with a modern scientific understanding of how complexity arises in the natural world, and as a philosophy that supports religious naturalism. A longer compilation of emergent forms in nature is the 2004 book by biologist Harold Morowitz: The Emergence of Everything.
Emergentists have suggested that the mind-body problem is better accounted for in emergentist terms. Jaegwon Kim, by contrast, has said that a problem for emergentism is “causal closure” in a universe that does not allow for a mind-to-body causation. Emergentists, however, do not see the mind as something different from “the body” – but rather as something with properties uniquely its own. If these properties can exercise downward causation, it may be that there is no problem here. (This issue remains especially controversial.) However, the problem of mind-body interaction is at least as serious a problem for reductive physicalism, leading many reductive physicalists to deny the very existence of mind through a lack of alternatives.
John Stuart Mill
John Stuart Mill outlined his version of emergentism in System of Logic (1843). Mill argued that the properties of some physical systems, such as those in which dynamic forces combine to produce simple motions, are subject to a law of nature he called the “Composition of Causes“. According to Mill, emergent properties are not subject to this law, but instead amount to more than the sums of the properties of their parts.
Mill believed that various chemical reactions (poorly understood in his time) could provide examples of emergent properties, although some critics believe that modern chemistry has shown that these reactions can be given satisfactory reductionist explanations. This raises the possibility that the emergentist position is more a matter of epistemology than metaphysics.
More recently, however, physicist Erwin Schrodinger in his highly acclaimed work “What is Life?” pointed out that chemical isomers, which are composed of precisely the same individual atoms, though differently arranged, sometimes have similar properties and sometimes have completely different properties. This would seem to suggest that the emergentist position which Schrödinger argues is more a matter of metaphysics than epistemology. (See, at the isomer link previously cited, the differences between theobromine and theophylline.)
C. D. Broad
British philosopher C. D. Broad defended a realistic epistemology in The Mind and its Place in Nature (1925) arguing that emergent materialism is the most likely solution to the mind-body problem. Broad’s definition of emergence amounted to the claim that mental properties would count as emergent if and only if philosophical zombies were metaphysically possible. Many philosophers take this position to be inconsistent with some formulations of psychophysical supervenience.
C. Lloyd Morgan and Samuel Alexander
Samuel Alexander‘s views on emergentism, argued in Space, Time, and Deity (1920), were inspired in part by the ideas in psychologist C. Lloyd Morgan‘s Emergent Evolution. Alexander believed that emergence was fundamentally inexplicable, and that emergentism was simply a “brute empirical fact”:
“The higher quality emerges from the lower level of existence and has its roots therein, but it emerges therefrom, and it does not belong to that level, but constitutes its possessor a new order of existent with its special laws of behaviour. The existence of emergent qualities thus described is something to be noted, as some would say, under the compulsion of brute empirical fact, or, as I should prefer to say in less harsh terms, to be accepted with the “natural piety” of the investigator. It admits no explanation.” (Space, Time, and Deity)
Despite the causal and explanatory gap between the phenomena on different levels, Alexander held that emergent qualities were not epiphenomenal. His view can perhaps best be described as a form of nonreductive physicalism (NRP) or supervenience theory.
Ludwig von Bertalanffy
Ludwig von Bertalanffy founded General System Theory (GST), which is a more contemporary approach to emergentism. A popularization of many of the elements of GST may be found in The Web of Life by Fritjof Capra.
- Laughlin, Robert B. A Different Universe. 2005.
- Emergentism in the Stanford Encyclopedia of Philosophy, 2007.
- Emergentism in the Dictionary of Philosophy of Mind, 2007.