The failures of phlogiston and vitalism are historical hindsight. Dare I step out on a limb, and name some current theory which I deem analogously flawed?
I name emergence or emergent phenomena—usually defined as the study of systems whose high-level behaviors arise or “emerge” from the interaction of many low-level elements. (Wikipedia: “The way complex systems and patterns arise out of a multiplicity of relatively simple interactions.”)
Taken literally, that description fits every phenomenon in our universe above the level of individual quarks, which is part of the problem. Imagine pointing to a market crash and saying “It’s not a quark!” Does that feel like an explanation? No? Then neither should saying “It’s an emergent phenomenon!”
It’s the noun “emergence” that I protest, rather than the verb “emerges from.” There’s nothing wrong with saying “X emerges from Y,” where Y is some specific, detailed model with internal moving parts. “Arises from” is another legitimate phrase that means exactly the same thing. Gravity arises from the curvature of spacetime, according to the specific mathematical model of General Relativity. Chemistry arises from interactions between atoms, according to the specific model of quantum electrodynamics.
Now suppose I should say that gravity depends on “arisence” or that chemistry is an “arising phenomenon,” and claim that as my explanation.
The phrase “emerges from” is acceptable, just like “arises from” or “is caused by” are acceptable, if the phrase precedes some specific model to be judged on its own merits.
However, this is not the way “emergence” is commonly used. “Emergence” is commonly used as an explanation in its own right.
I have lost track of how many times I have heard people say, “Intelligence is an emergent phenomenon!” as if that explained intelligence. This usage fits all the checklist items for a mysterious answer to a mysterious question. What do you know, after you have said that intelligence is “emergent”? You can make no new predictions. You do not know anything about the behavior of real-world minds that you did not know before. It feels like you believe a new fact, but you don’t anticipate any different outcomes. Your curiosity feels sated, but it has not been fed. The hypothesis has no moving parts—there’s no detailed internal model to manipulate. Those who proffer the hypothesis of “emergence” confess their ignorance of the internals, and take pride in it; they contrast the science of “emergence” to other sciences merely mundane.
And even after the answer of “Why? Emergence!” is given, the phenomenon is still a mystery and possesses the same sacred impenetrability it had at the start.
A fun exercise is to eliminate the adjective “emergent” from any sentence in which it appears, and see if the sentence says anything different:
- Before: Human intelligence is an emergent product of neurons firing.
- After: Human intelligence is a product of neurons firing.
- Before: The behavior of the ant colony is the emergent outcome of the interactions of many individual ants.
- After: The behavior of the ant colony is the outcome of the interactions of many individual ants.
- Even better: A colony is made of ants. We can successfully predict some aspects of colony behavior using models that include only individual ants, without any global colony variables, showing that we understand how those colony behaviors arise from ant behaviors.
Another fun exercise is to replace the word “emergent” with the old word, the explanation that people had to use before emergence was invented:
- Before: Life is an emergent phenomenon.
- After: Life is a magical phenomenon.
- Before: Human intelligence is an emergent product of neurons firing.
- After: Human intelligence is a magical product of neurons firing.
Does not each statement convey exactly the same amount of knowledge about the phenomenon’s behavior? Does not each hypothesis fit exactly the same set of outcomes?
“Emergence” has become very popular, just as saying “magic” used to be very popular. “Emergence” has the same deep appeal to human psychology, for the same reason. “Emergence” is such a wonderfully easy explanation, and it feels good to say it; it gives you a sacred mystery to worship. Emergence is popular because it is the junk food of curiosity. You can explain anything using emergence, and so people do just that; for it feels so wonderful to explain things.
Humans are still humans, even if they’ve taken a few science classes in college. Once they find a way to escape the shackles of settled science, they get up to the same shenanigans as their ancestors—dressed up in the literary genre of “science,” but humans are still humans, and human psychology is still human psychology.
In line with previous comments, I'd always understood the idea of emergence to have real content: "systems whose high-level behaviors arise or 'emerge' from the interaction of many low-level elements" as opposed to being centrally determined or consciously designed (basically "bottom-up" rather than "top-down"). It's not a specific explanation in and of itself, but it does characterise a class of explanations, and, more importantly, excludes certain other types of explanation.
This comment hits the bullseye. The general idea of emergence is primarily useful is in pointing out that when we don't understand something, there are still alternative explanations to those that superstitiously posit a near-omniscience or that pretend to have information or an ability to model complex phenomena that one does not in fact have. So, for example, a highly improbable organism does not imply a creator, a good law does not imply a legislator, a good economy does not require an economic planner, and so on, because such things can be generated by emergent processes. To come to such a conclusion does not require that we have first reasoned out the specific process by which the object in question emerged. Indeed if we had, we wouldn't have to invoke emergence any more but rather some more specific algorithm, such as natural selection to explain the origins of species.
For this reason, I strongly disagree with the following definition
Let K(.) be Kolmogorov complexity. Assume you have a system M consisting of and fully determined by n small identical parts C. Then M is 'emergent' if M can be well approximated by an object M' such that K(M') << n*K(C).
Because it is just in situations where a phenomenon has a not highly reducible complexity -- where M is not fully determined by n small identical particles, or where it is but K(M') is not substantially smaller than n*K(C) -- that the idea that a phenomenon is emergent, rather than the product of a near-omniscient or near-omnipotent creator, is most useful.
I'd add that the belief that any important phenomenon is highly reducible, or that even if it is reduceable that humans are capable of undertaking that reduction, are two other species of superstition. These are just as pernicious as the related superstition of the near-omniscient creator. In many, perhaps most cases of interest we either have to be satisfied with regarding a phenomenon as "emergent" or we have to superstitiously pretend that some being has information or a capability of reduction that it does not in fact have.