Editing Emergence (section)

==In philosophy==
{{Main|Emergentism}}
Philosophers often understand emergence as a claim about the [[etiology]] of a [[system]]'s properties. An emergent property of a system, in this context, is one that is not a property of any component of that system, but is still a feature of the system as a whole. [[Nicolai Hartmann]] (1882–1950), one of the first modern philosophers to write on emergence, termed this a ''categorial novum'' (new category).<ref>{{cite book |last=Hartmann |first=Nicolai |url=https://doi.org/10.1515/9783110246681 |title=Possibility and actuality |date=2013 |publisher=Walter De Gruyter |isbn=9783110246681 |page=223 |translator-last1=Adair |translator-first1=Stephanie |translator-last2=Scott |translator-first2=Alex |doi=10.1515/9783110246681 |quote=The higher nexus is, in many of its structural elements, dependent on the lower, but is autonomous in its particular nature (its categorial ''novum''). The chain of conditions of a real thing in the higher stratum contains an ample number of components from the lower strata; but they are only partial aspects of it, and therefore do not make its real possibility complete; they make it, in fact, neither necessary nor actual. The chain becomes complete only through the addition of real components of its own stratum. But these are under a categorially different kind of determination. Structurally, they belong to the higher real nexus itself, and are not found outside of it.}}</ref>

===Definitions===
This concept of emergence dates from at least the time of [[Aristotle]].<ref name="Meta">Aristotle, ''[[Metaphysics (Aristotle)]]'', Book VIII (Eta) 1045a 8–10: "... the totality is not, as it were, a mere heap, but the whole is something besides the parts ...", i.e., the whole is other than the sum of the parts.</ref> Many scientists and philosophers<ref>
{{cite book
 | last1 = Winning
 | first1 = Jason
 | last2 = Bechtel
 | first2 = William
 | author-link2 = William Bechtel
 | chapter = Being emergence vs. pattern emergence: complexity, control, and goal-directedness in biological systems
 | chapter-url = https://philpapers.org/rec/WINBEV
 | editor1-last = Gibb
 | editor1-first = Sophie
 | editor2-last = Hendry
 | editor2-first = Robin Findlay
 | editor3-last = Lancaster
 | editor3-first = Tom
 | title = The Routledge Handbook of Emergence
 | url = https://books.google.com/books?id=0Tz3DwAAQBAJ
 | series = Routledge Handbooks in Philosophy
 | location = Abingdon
 | publisher = Routledge
 | date = 2019
 | page = 134
 | isbn = 9781317381501
 | access-date = 25 October 2020
 | quote = Emergence is much discussed by both philosophers and scientists.
}}
</ref>  have written on the concept, including [[John Stuart Mill]] (''[[Composition of Causes]]'', 1843)<ref>"The chemical combination of two substances produces, as is well known, a third substance with properties entirely different from those of either of the two substances separately, or of both of them taken together."</ref> and [[Julian Huxley]]<ref>Julian Huxley: "now and again there is a sudden rapid passage to a totally new and more comprehensive type of order or organization, with quite new emergent properties, and involving quite new methods of further evolution" {{Harv|Huxley|Huxley|1947|p=120}}</ref> (1887–1975).

The philosopher [[George Henry Lewes|G. H. Lewes]] coined the term "emergent" in 1875, distinguishing it from the merely "resultant":

<blockquote>Every resultant is either a sum or a difference of the co-operant forces; their sum, when their directions are the same – their difference, when their directions are contrary. Further, every resultant is clearly traceable in its components, because these are [[homogeneous]] and [[Commensurability (philosophy of science)|commensurable]]. It is otherwise with emergents, when, instead of adding measurable motion to measurable motion, or things of one kind to other individuals of their kind, there is a co-operation of things of unlike kinds. The emergent is unlike its components insofar as these are incommensurable, and it cannot be reduced to their sum or their difference.<ref>
{{cite book
 | last1 = Lewes
 | first1 = George Henry
 | author-link1 = George Henry Lewes
 | title = Problems of Life and Mind
 | url = https://books.google.com/books?id=0J8RAAAAYAAJ
 | series = First Series: The Foundations of a Creed
 | volume = 2
 | location = Boston
 | publisher = Osgood
 | date = 1875
 | page = 369
 | access-date = 24 Mar 2019
}}
</ref>{{sfn|Blitz|1992}}
</blockquote>
===Strong and weak emergence===
{{further|Emergent materialism|Reductive materialism}}
Usage of the notion "emergence" may generally be subdivided into two perspectives, that of "weak emergence" and "strong emergence". One paper discussing this division is ''Weak Emergence'', by philosopher [[Mark Bedau]]. In terms of physical systems, weak emergence is a type of emergence in which the emergent property is amenable to computer simulation or similar forms of after-the-fact analysis (for example, the formation of a traffic jam, the structure of a flock of starlings in flight or a school of fish, or the formation of galaxies). Crucial in these simulations is that the interacting members retain their independence. If not, a new entity is formed with new, emergent properties: this is called strong emergence, which it is argued cannot be simulated, analysed or reduced.{{sfn|Bedau|1997}}

[[David Chalmers]] writes that emergence often causes confusion in philosophy and science due to a failure to demarcate strong and weak emergence, which are "quite different concepts".<ref> Chalmers, David J. (2002). "Strong and Weak Emergence" [http://consc.net/papers/emergence.pdf] Republished in P. Clayton and P. Davies, eds. (2006) ''The Re-Emergence of Emergence''. Oxford: Oxford University Press</ref>

Some common points between the two notions are that emergence concerns new properties produced as the system grows, which is to say ones which are not shared with its components or prior states. Also, it is assumed that the properties are [[supervenient]] rather than metaphysically primitive.{{sfn|Bedau|1997}}

Weak emergence describes new properties arising in systems as a result of the interactions at a fundamental level. However, Bedau stipulates that the properties can be determined only by observing or simulating the system, and not by any process of a [[Reductionism|reductionist]] analysis. As a consequence the emerging properties are '''scale dependent''': they are only observable if the system is large enough to exhibit the phenomenon. Chaotic, unpredictable behaviour can be seen as an emergent phenomenon, while at a microscopic scale the behaviour of the constituent parts can be fully [[Deterministic system|deterministic]].{{cn|date=June 2024}}

[[Mark Bedau|Bedau]] notes that weak emergence is not a universal metaphysical solvent, as the hypothesis that [[consciousness]] is weakly emergent would not resolve the traditional [[Philosophy of mind|philosophical questions]] about the physicality of consciousness. However, Bedau concludes that adopting this view would provide a precise notion that emergence is involved in consciousness, and second, the notion of weak emergence is metaphysically benign.{{sfn|Bedau|1997}}

Strong emergence describes the direct causal action of a high-level system on its components; qualities produced this way are [[irreducible (philosophy)|irreducible]] to the system's constituent parts.{{sfn|Laughlin|2005}} The whole is other than the sum of its parts. It is argued then that no simulation of the system can exist, for such a simulation would itself constitute a reduction of the system to its constituent parts.{{sfn|Bedau|1997}} Physics lacks well-established examples of strong emergence, unless it is interpreted as the impossibility ''in practice'' to explain the whole in terms of the parts. Practical impossibility may be a more useful distinction than one in principle, since it is easier to determine and quantify, and does not imply the use of mysterious forces, but simply reflects the limits of our capability.<ref>{{cite book|last= Luisi|first= Pier L.|title= The Emergence of Life: From Chemical Origins to Synthetic Biology|year= 2006|publisher= Cambridge University Press|location= Cambridge, England|isbn= 978-0521821179|page= 119|url= http://www.cambridge.org/us/academic/subjects/chemistry/organic-chemistry/emergence-life-chemical-origins-synthetic-biology|url-status=live|archive-url= https://web.archive.org/web/20151117023700/http://www.cambridge.org/us/academic/subjects/chemistry/organic-chemistry/emergence-life-chemical-origins-synthetic-biology|archive-date= 2015-11-17}}</ref>

====Viability of strong emergence====
One of the reasons for the importance of distinguishing these two concepts with respect to their difference concerns the relationship of purported emergent properties to science. Some thinkers question the plausibility of strong emergence as contravening our usual understanding of physics. Mark A. Bedau observes:

{{blockquote|Although strong emergence is logically possible, it is uncomfortably like magic. How does an irreducible but supervenient downward causal power arise, since by definition it cannot be due to the aggregation of the micro-level potentialities? Such causal powers would be quite unlike anything within our scientific ken. This not only indicates how they will discomfort reasonable forms of materialism. Their mysteriousness will only heighten the traditional worry that emergence entails illegitimately getting something from nothing.{{sfn|Bedau|1997}}}}

The concern that strong emergence does so entail is that such a consequence must be incompatible with metaphysical principles such as the [[principle of sufficient reason]] or the Latin dictum ''ex nihilo nihil fit'', often translated as "nothing comes from nothing".<ref>{{cite web |author=<!-- not stated --> |title=EX NIHILO NIHIL FIT Definition & Meaning |url=https://www.merriam-webster.com/dictionary/ex%20nihilo%20nihil%20fit |website=merriam-webster.com |publisher=Encyclopaedia Britannica company |access-date= 27 April 2025}}</ref>

Strong emergence can be criticized for leading to causal [[overdetermination]]. The canonical example concerns emergent mental states (M and M∗) that supervene on physical states (P and P∗) respectively. Let M and M∗ be emergent properties. Let M∗ supervene on base property P∗. What happens when M causes M∗? [[Jaegwon Kim]] says:

{{blockquote|In our schematic example above, we concluded that M causes M∗ by causing P∗. So M causes P∗. Now, M, as an emergent, must itself have an emergence base property, say P. Now we face a critical question: if an emergent, M, emerges from basal condition P, why cannot P displace M as a cause of any putative effect of M? Why cannot P do all the work in explaining why any alleged effect of M occurred? If causation is understood as [[nomological]] (law-based) sufficiency, P, as M's emergence base, is nomologically sufficient for it, and M, as P∗'s cause, is nomologically sufficient for P∗. It follows that P is nomologically sufficient for P∗ and hence qualifies as its cause...If M is somehow retained as a cause, we are faced with the highly implausible consequence that every case of downward causation involves overdetermination (since P remains a cause of P∗ as well). Moreover, this goes against the spirit of emergentism in any case: emergents are supposed to make distinctive and novel causal contributions.<ref>{{cite journal | last1 = Kim | first1 = Jaegwon | year = 2006 | title = Emergence: Core ideas and issues | journal = Synthese | volume = 151 | issue = 3| pages = 547–59 | doi = 10.1007/s11229-006-9025-0 | s2cid = 875121 }}</ref>}}

If M is the cause of M∗, then M∗ is overdetermined because M∗ can also be thought of as being determined by P. One escape-route that a strong emergentist could take would be to deny [[downward causation]]. However, this would remove the proposed reason that emergent mental states must supervene on physical states, which in turn would call [[physicalism]] into question, and thus be unpalatable for some philosophers and physicists.

Carroll and Parola propose a taxonomy that classifies emergent phenomena by how the macro-description relates to the underlying micro-dynamics.<ref name="CP">{{cite journal |last1=Carroll |first1=Sean M. |last2=Parola |first2=Achyuth |year=2024 |title=What Emergence Can Possibly Mean |url=https://philarchive.org/rec/CARWEC-6 |pages=1–23|arxiv=2410.15468 }}</ref>

; Type‑0 (Featureless) Emergence:
: A coarse-graining map Φ from a micro state space ''A'' to a macro state space ''B'' that commutes with time evolution, without requiring any further decomposition into subsystems.

; Type‑1 (Local) Emergence:
: Emergence where the macro theory is defined in terms of localized collections of micro-subsystems. This category is subdivided into:
:: Type‑1a (Direct) Emergence: When the emergence map Φ is algorithmically simple (i.e. compressible), so that the macro behavior is easily deduced from the micro-states.
:: Type‑1b (Incompressible) Emergence: When Φ is algorithmically complex (i.e. incompressible), making the macro behavior appear more novel despite being determined by the micro-dynamics.

; Type‑2 (Nonlocal) Emergence:
: Cases in which both the micro and macro theories admit subsystem decompositions, yet the macro entities are defined nonlocally with respect to the micro-structure, meaning that macro behavior depends on widely distributed micro information.

; Type‑3 (Augmented) Emergence:
: A form of strong emergence in which the macro theory introduces additional ontological variables that do not supervene on the micro-states, thereby positing genuinely novel macro-level entities.

===Objective or subjective quality===
Crutchfield regards the properties of complexity and organization of any system as [[Subjectivity|subjective]] [[Quality (philosophy)|qualities]] determined by the observer.

<blockquote>Defining structure and detecting the emergence of complexity in nature are inherently subjective, though essential, scientific activities. Despite the difficulties, these problems can be analysed in terms of how model-building observers infer from measurements the computational capabilities embedded in non-linear processes. An observer's notion of what is ordered, what is random, and what is complex in its environment depends directly on its computational resources: the amount of raw measurement data, of memory, and of time available for estimation and inference. The discovery of structure in an environment depends more critically and subtly, though, on how those resources are organized. The descriptive power of the observer's chosen (or implicit) computational model class, for example, can be an overwhelming determinant in finding regularity in data.<ref>
{{cite journal
| last1                 = Crutchfield
| first1                = James P.
| author-link1          = James P. Crutchfield
| year             = 1993
| title                 = The Calculi of Emergence: Computation, Dynamics, and Induction
| url                   = http://csc.ucdavis.edu/~cmg/compmech/pubs/CalcEmergTitlePage.htm
| journal               = Physica
| location     = Utrecht
| publication-date      = 1994
| volume                = 75
| issue                 = 1–3
| pages                  = 11–54
| access-date           = 24 Mar 2019
| bibcode = 1994PhyD...75...11C
| doi = 10.1016/0167-2789(94)90273-9
| url-access= subscription
}}
</ref>
</blockquote>

The low [[entropy]] of an ordered system can be viewed as an example of subjective emergence: the observer sees an ordered system by ignoring the underlying microstructure (i.e. movement of molecules or elementary particles) and concludes that the system has a low entropy.<ref>
See f.i. Carlo Rovelli: The mystery of time, 2017, part 10: Perspective, p.105-110
</ref>
On the other hand, chaotic, unpredictable behaviour can also be seen as subjective emergent, while at a microscopic scale the movement of the constituent parts can be fully deterministic.