Editing Emergence (section)

====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.