Editing Emergence (section)

===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.