Hmm, interesting. I've never actually realized that people used "emergent behavior" as a model or an explanation for anything. In that context, I'd always treated it as just a description, with the meaning that an "emergent phenomenon" is a "complex or seemingly complex phenomenon arising from interactions of a large number of very simple subparts," or something of the sort. Never thought of it as a model or an explanation, but just as a reasonable descriptive word. But if it is used as an attempted explanation to end discussion, then it's just functioning as a curiosity-stopper and should be questioned further.

Eliezer: I generally like your posts, but I disagree with you here. I think that there's at least one really useful definition of the word emergence (and possibly several useless ones).

It's true, of course (at least to a materialist like me), that every phenomenon emerges from subatomic physics, and so can be called 'emergent' in that sense. But if I ask you why you made this post, your answer isn't going to be, "That's how the quarks interacted!" Our causal models of the world have many layers between subatomic particles and perceived phenomena. Emergence refers to the relationship between a phenomenon and its immediate cause.

So, for instance, suppose I'm on the interstate and I get caught in a traffic jam. I might wonder why there's a huge jam on the road. It's possible that there's a simple, straightforward explanation: "There's a ten-car pileup a mile further on, and five of the six lanes are shut down. That's why there's a traffic jam." Obviously we could get far more reductionist— both in terms of "why is there a pileup" and "why does a pileup cause a traffic jam"—but for the conceptual level we're operating on, the pileup is a full and complete answer. And thus the traffic jam isn't an 'emergent' phenomenon; it has one major identifiable cause.

In contrast, a lot of traffic jams 'just happen.' The previous sentence is false, strictly speaking; the jams come from somewhere. But you can't point to an individual cause of them; they arise from the local effects of millions of local actions taken by individual drivers. Removing any one of these actions wouldn't eliminate the jam; it's a cumulative product of all of them. So people searching for an explanation of why it takes two hours to dive ten miles in rush hour get really frustrated, because there's no good explanation to give them. And people trying to fix rush hour get even more frustrated, because there's no good angle to attack the problem from.

So emergence, in this sense, means that a phenomenon has many intertwined causes, rather than one or two identifiable and major causes. It turns out, of course, that most interesting phenomena are emergent (non-emergent phenomena are, by definition, boring, since their causes are straightforward). But "emergence" is useful as a shorthand for "the causes are complicated and interconnected, and I can't pick one out and tell you, 'here it is, this is why that happened.'" It's important not to get confused, and not to think an explanation of why we don't understand something is the same as an explanation of that thing. But as long as you remember that, it's a useful thing to remember.

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.

I would think that something like "life/intelligence is an emergent phenomenon" means "you don't need intelligent design to explain life/intelligence".

Okay, but that's really not how I have understood emergence. It delineates a subject matter, and does so in an abstract way that includes many specific examples which are purportedly alike in some important way. But I don't think this use necessarily implies that the explanation has thereby been given. It is, rather, usually an attempt to delineate a subject matter which can be further investigated. I believe that the hope is that a general theory of emergence is possible, though my impression is that there isn't even a generally agreed-upon definition of it, let alone a commonly accepted theory.

One common element that I have sometimes noticed is that an emergent phenomenon can be idealized and a simplified mathematical model constructed of it, which is not precisely correct but which is a very good approximation. The existence of such simple and very good models is remarkable and extremely lucky for us.

For example, an actual fluid such as water is really made up of molecules that interact, but there is a simple mathematical model for fluids which treats fluids as absolutely continuous and smooth all the way down, not composed of atoms but fluid at every scale. As I vaguely recall, this simple mathematical model can be adjusted by plugging in values for viscosity, compressibility, and so forth. It is not exactly the same as actual fluids (the resemblance breaks down completely on the scale of molecules) but it is very close at the macroscopic scale.

Similarly, we have the concept of the "ideal gas", which is only an approximation to real gases but on a macroscopic scale a very close and useful one.

That we can vastly simplify and idealize something without losing all that much predictive power seems to be a characteristic of many so-called emergent phenomena.

Eliezer apparently travels in different circles than I do, and encounters people who use the word "emergence" very differently. Here is the kind of situation where I usually hear the word "emergence" used:

Me: Well, I think I'll build an AI that understands Chinese this weekend.

Philosopher: Build it from what?

Me: NAND gates, I suppose.

Philosopher: That's impossible. Searle proved it. NAND gates don't understand Chinese, even a little. So a collection of lots of NAND gates can't understand Chinese either.

Me: Huh? Searle and you don't get it. The understanding of Chinese is going to be an emergent property of the whole complex system.

Philosopher: "Emergence! Aaarghh!"

Me: Would you like me to explain the code to you?

Philosopher: No, thanks. I don't know anything about programming. But I do know that the word "Emergence" is a sure sign of messed up thinking.

In other words, I don't consider "emergence" as an inoculation against curiosity. I consider it an inoculation against stupidity. It is a claim by a reductionist that a high level phenomenon can be constructed from low-level machinery which is different in kind.

Most scientists I know use 'emergence" as I do. But I have to admit that most philosophers I know use it as Eliezer does. I guess we will just have to agree to dis- ... err, agree to miscommunicate. But I do wish that Eliezer would stop pretending that the word "emergence" has to have an explanatory function in order to be useful. It has a classificatory function. It collects together a class of models which have in common the property that naive reductionists fail to understand them. It is classification, not explanation. Putting the shoe on the other foot:

Philosopher: Your argument is fallacious.

Me: Aaarghh! "Fallaciousness" How does that explain how my argument is wrong. You are just trying to stop conversation.

Philosopher: But... But... You don't understand. Fallaciousness is not being used as an explanation.

There were some good comments on this thread, but I needed to add my own two cents.

As Eliezer requested, I offer my view on what emergence isn't: emergence is not an explanation. When I say that a phenomenon is emergent, I am using a shorthand to say that I understand the basic rules, but I can't form even a simple model of how they result in the phenomenon.

Take, for example, Langton's Ant. The ant crawls around on an infinite grid of black and white squares, turning right at the centre of each white square and left ant the centre of each black square, and flipping the colour of the square it's in each time it turns.

The first few hundred steps create simple patterns that are often symmetric, but after that the patterns Langton's Ant produces become pseudorandom. If left to run for around 10000 steps, the Ant builds a highway - that is, it falls into a pattern of 104 of steps, and at the end of each cycle, it has moved diagonally and the cycle repeats. After millions of steps, the grid has a diagonal streak across it. As far as we know, the Ant always builds a highway.

Highways are emergent by the definition I use - that is, I know exactly how Langton's Ant works, and therefore, in theory, know why it builds a highway, but I can't form a model of its behaviour that I can actually use. I simply do not have a good enough brain to actually run Langton's Ant. By this definition, conciousness is an emergent phenomenon (I know it's caused by neurons, but I have no idea how) but the behaviour of gases is not (I know the ideal gas law and its predictions seem reasonable if I imagine a manageable number of molecules bumping about).

By my definition, emergent is much like blue. "It's emergent!" and "It's blue!" are both mysterious answers if I asked for an explanation, but useful answers if I asked for a description.

Here is David Chalmer's short philosophical stab at what emergence is and ain't.

Aren't superconductivity and ferromagnetism perfect examples of emergent phenomena?

Yes. So are non-superconductivity and non-ferromagnetism. That's the problem.

I do think there is a good deal of commonality among the reasonable comments about what emergence is and also feel the force of Eliezer's request for negative examples.

I'll try to summarize (and of course over-simplify).

When we have a large collection of interacting elements, and we can measure a property of the collection as a whole, in some cases we'd like to call that property emergent, and in some cases we wouldn't.

I can think of three important cases:

• If we can compute the property as a simple sum or average of properties of the individual elements, then it is not emergent. So e.g. mass or temperature are not emergent properties.


• If we need to analyze long chains of structurally specific causal interactions to explain the coarser grained property, then it is not emergent. So e.g. the time telling properties of a mechanical clock, or the arithmetic computing properties of a calculator are not emergent.


• If we can compute the property as a function of the properties of the elements, and it depends sensitively on specific characteristics of their behavior and interaction, but is robust under local perturbations (i.e. doesn't depend on structurally specific causal chains), then the property is emergent. So e.g. percolation is emergent. Also we have some warrant to say that flocking, thinking (as brains do it), social interaction, etc. are emergent.

I'm not claiming these three cases cover all the legitimate positive and negative examples of emergence -- I don't think the concept has crystallized that completely yet. But I do think they answer Eliezer's challenge.

Another, less crisply defined question is whether we should be using "emergence" so defined, and relatedly, whether people are mostly trying to use it in this sense, or whether they are, as Eliezer fears, just using it as a synonym for "magic".

My own feeling is that many users of the term are groping for a clear definition of this general sort, and that they are doing so precisely to avoid having to explain a large class of phenomena by "magic".

Eliezer: Here's another example similar to ones other people have raised, a story I heard once, that might explain why I think it's an important and useful concept.

Supposedly, in the early nineties when the Russians were trying to transition to a capitalist economy, a delegation from the economic ministry went to visit England, to see how a properly market-based economy would work. The British took them on a tour, among other things, of an open-air fresh foods market. The Russians were shown around the market, and were appropriately impressed. Afterwards, one of the senior delegation members approached one of his escorts: "So, who sets the price for rice in this market?" The escort was puzzled a bit, and responded, "No one sets the price. It's set on the market." And the Russian responded, "Yes, yes, I know, of course that's the official line. But who really sets the price of rice?"

The Russian couldn't conceive that an organization as complex as the open air market could have assembled itself; he was sure someone must have designed it in order for it to work. It had to have been set up. But markets and prices are an emergent phenomenon; the price isn't set by one person and doesn't have any one cause. And yet the markets function.

Similarly, a lot of people seem to have a mental model of democratic institutions that says it's a non-emergent phenomenon: if you write a constitution and hold elections, you get a democracy with the rule of law. Others (including myself) claim that democracy and rule-of-law are emergent phenomena: if they don't exist, there's no specific set of actions a central actor can take that will cause them to exist. They exist because of millions of decentralized and uncoordinated actions of individuals without specific direction. If you hold the first view, projects like the establishment of the new Iraqi government make sense: we set up a government with a constitution and elections, so it should become a free democratic state. If you hold the second view, the project is insane: freedom and democracy require millions of individual and low-level cultural shifts that can't be imposed from above, so there's no way for us to turn the nation into a democracy. My point here isn't that one view is right or wrong, although I have a firm belief. My point is that it's highly relevant to our foreign policy to ask whether democracy is emergent or not.

Usually when you say, "You can't just impose X from above," you're claiming X is an emergent phenomenon; the hallmark of a non-emergent phenomenon is that it's possible for a single actor to take a series of actions that either cause or prevent it.

I don't buy the analogy between emergence and phlogiston or vitalism. Offering up "emergence!" as an explanation of a phenomenon is a category mistake, to be sure, and is a semantic stopsign when misunderstood this way.

As other commenters have noted, however, there is a proper understanding of emergence that is useful. (In philosophy, for instance, it's an admittedly sloppy but still useful term to classify different kinds of explanations of consciousness). This doesn't seem true of explanations that appeal to phlogiston or vitalism. Vitalist explanations aren't category mistakes. They're simply vacuous explanations, full stop.

In most of the contexts in which I have seen the word "emergent used", it has signified a lack of understanding of the underlying causes of the phenomenon being described but rather than acting as a semantic stop-sign seemed to be used as its exact oppposite - as a marker for an area sufficiently interesting to be deserving of further research with a view to eventual full explanation. But perhaps I've been misunderstanding the intent of the authors.

Creeping into his soul, he felt the first faint tinges of despair.

After all these posts on how the strength of an idea is what it excludes, forbids, prohibits, people are still citing positive examples as proof of the power of emergence? Tell me what it isn't!

I remember when Warren Spector & Harvey Smith were going on about emergence in videogames. I think their definition was something like "a non-obvious [it may even surprise the designers] outcome of a system of rules rather than something scripted". That's a rather subjective definition but it seems to fit as well for the things that are described as "emergent" in real life. Since life is not actually a videogame but has universally valid rules, it would not be a very useful concept for that domain. I think Wolfram has written a lot about that sort of thing, but I don't actually know much about what it is he says other than that its an important idea.

What are phenomena that aren't "emergent"? I guess Eliezer is right when he says "a single quark". I think Eliezer makes a good case that the word is overused, and doesn't enlighten the discourse.

It might be more useful to describe things in reverse " X are the components of phenomenon Y". Such as "Neurons firing are the known components of intelligence". Because when we observe something, it can be useful to ask "what are its components"?

It contrast, everything observed IS the component of some bigger system, but it can be also useful to ask, what is the next biggest ordered system it is a part of, etc. That's where "emergent phenomena" might legitmately come in. Because an ant colony might be the next biggest ordered system that an individual ant is a part of, and that does seem like useful information.

Most of this is specific to videogames and probably will not be applicable anywhere else:

An emergent property in the context of videogames is one the designers of the game did not intend, [more strictly: yet is not a programming error].

Excluding the possibly, since this example is ambiguous using it:

In the game Super Smash Bros, jumping is not emergent, since the designers programmed it into the game specifically.

Wavedashing [dodging into the ground so that you will be able to move while attacking] (and in fact, every single bit of strategy for every character) is emergent; it's not programmed into the game, it's just that if you put together all the intended rules of the game, wavedashing appears also.

What does "this is emergent" tell you, in this context?

It tells you first of all it's unintentional, which then tells you it has a vastly greater chance of being unbalanced or broken.

Using the stricter definition, it also tells you whatever it is profits the player in some way, because if it did not profit the player in some way it would not have emerged; someone would have found it, not used it or told anyone, and it would just fade away. (But this is only valid for emergent things when they're structured in a certain way. This part can be generalized to, say, the economy, but not, say, to traffic jams, because traffic jams are more tragedy of the commons types of things.)

It also tells you, most importantly, that it is probably not possible to know all the specific causes of this thing and instead to try wide and general causes. (i.e: "World War I happened because of a general attitude among nations that military force was a good way to solve problems." It's possible to say it happened "because Alice thought... and Bob thought... but Carol thought... and Dave thought....", but this is going to be either much less accurate or not worth the effort to make it accurate.)

What does "this is non-emergent" tell you?

There are one or more obvious specific causes that it would not be worth breaking down. (In the case of videogames, the developers, but it also works for cases like "there is a big dent in the front of my car because I crashed it into a tree" [but wait, you say, isn't that also phrasable as "because the force from the tree caused this molecule and this molecule and this molecule to move backwards"? Yes, but it doesn't matter; the only cause is still the force from the tree.])

(Finally, random other example I thought of after reading the Go example:

In chess, the position of the pieces at the beginning of the game is not emergent: there is one cause for that: because it's part of the rules of the game.

The fact that the best first move for white in most cases is pawn to e4 is emergent. Nobody wrote that into the rules of chess; it's just a consequence of the positions of the pieces.)

I'm getting the feeling that Eliezer is starting to get overly eager to attack semantic stopsigns. I recommend magic oil in the evening and emergent phenomena in the morning.

My impression of "emergence" was that it's closely related to pattern recognition. You have atoms A, B..ZZZZZZZZZZ, and you recognize that these atoms form a certain pattern. So you say that a supercluster of galaxies/bar stool/intelligence "emerges" from a bunch of atoms.

I once had a prolonged debate with an anticognitivist. He, as usual, argued that no matter what kind of AI you build, if you take it apart, it's just "switches flipping". In that debate, I maintained that intelligence does not require anything else - it emerges from switches flipping the same way that Firefox emerges from switches flipping. Both are just human names for patterns that arise in a sea of subatomic particles.

[That was one frustrating debate... Both of us were equally bewildered that the other refuses to get it.]

The example of emergence that comes to my mind most readily is a simple observation that Douglas Hofstadter made in Godel, Escher, Bach -- a book which definitely does not use "emergent" as a synonym for "magical":

In a game of Go, once there are two separate open spaces -- "eyes" -- in the middle of a connected group of stones, that group becomes invincible (because the opponent can't fill both holes with one move). There's no official rule in Go that says "Patterns with two eyes can't be captured", the rule just says that to capture a group you have to surround it completely and leave no open spaces. Thus two-eye invincibility is an emergent consequence of the rules of Go.

It's important that this new emergent rule is a significant simplification: once you realize that two eyes are invincible, you no longer have to do any complicated analysis about how close a two-eyed group is to being completely surrounded. It's safe, full stop (at least as long as you don't stupidly fill in the holes yourself).

The game of Go has very few rules. In practice, the two-eye invincibility "rule" is a very important and useful one, if you want to play the game well. To try to force Eliezer to talk about "emergence" or something equivalent, I would ask: where did the two-eye invincibility rule come from?

-- Okay, now, so what isn't emergent? There's a another Go rule, the "ko" rule, which says you can't play in such a way as to get the exact same board position back after two moves: no capture followed by immediate recapture unless it changes the board. There's nothing "emergent" about that rule that I can think of -- it helps keep Go games from going on forever, but it has no simple-but-unexpected high-level consequences.

There are a lot of strategic patterns of play in Go that are not emergent, either -- e.g., there are no simple rules of thumb that can tell you, in all cases, whether a group with one eye or no eyes can be captured or not. Often the answer depends on a single apparently unrelated stone way over on the other side of the board. No simplifications available here, therefore no emergence.

There are many other more involved examples of emergence (and non-emergence) -- gliders and spaceships in Conway's Game of Life come to mind, and Herschels and random ash densities -- but this blog comment is too narrow to contain a good summary of them all...

Two other books that do a fine job (in my opinion) of describing the concept of "emergence" as distinct from "magic" are Cohen and Stewart's The Collapse of Chaos and Figments of Reality.

Eliezer: "Don't y'all find it a little suspicious that so many people think "emergence" is a useful concept, yet have different definitions of what it is?"

That's a non sequitur. Different people define intelligence differently, so what? The fact that they don't understand intelligence doesn't mean that it isn't a useful concept.

When people actually can't agree on the meaning of a word, the signnal to noise ratio drops from using it. But in that case, instead of discarding the word, people just need to standardize it.

An excellent example of a published paper against reductionism, using "emergence" in exactly this way such that it is indiscernible from "magic", is here:

http://philsci-archive.pitt.edu/3866/1/Tilburg_submission_fin.pdf

Well, I agree that that fake explanation is used too often, and that it only gets any cred because it's from the right literature genre. But I don't think the whole of work in emergence can really be reduced to a mystery to worship. Certainly "emergence" is a stupid noun, just like "Red-hood" is a stupid noun. And that's a wonderful exercise to shut up the anti-reductionist movement based around emergence.

But "emergently arising" and "arising" can be given useful different meanings without stretching things too far, specially if "emergent" is contrasted with "resultant".

The origin of the modern concept of emergence can be traced to the middle of the nineteenth century when realist philosophers first began pondering the deep dissimilarities between causality in the fields of physics and chemistry. The classical example of causality in physics is a collision between two molecules or other rigid objects. Even in the case of several colliding molecules the overall effect is a simple addition. If, for example, one molecule is hit by a second one in one direction and by a third one in a different direction the composite effect will be the same as the sum of the two separate effects: the first molecule will end up in the same final position if the other two hit it simultaneously or if one collision happens before the other. In short, in these causal interactions there are no surprises, nothing is produced over and above what is already there. But when two molecules interact chemically an entirely new entity may emerge, as when hydrogen and oxygen interact to form water. Water has properties that are not possessed by its component parts: oxygen and hydrogen are gases at room temperature while water is liquid. And water has capacities distinct from those of its parts: adding oxygen or hydrogen to a fire fuels it while adding water extinguishes it.

-- Manuel Delanda

Delanda is one of those anti-reductionists that I was talking about, but nonetheless I still think he gives useful and viable meanings to "emergent" and "resultant" here , though I think his arguments against reductionism are just plain silly. They leave room for reducing any "emergent property" of a whole to the interactions of its parts, so as far as I can tell his arguments leave plenty of room for reductionism.

The word 'emergence' is an accent, not an explanation. It shifts focus to the idea that the system itself contains enough power or complexity to produce the effects wanted, when the mistake is to assume that the system doesn't have it. Let's show a simplistic example with ant colonies:

Ant colonies exhibit intelligence.
Ant colonies exhibit intelligent emergent behavior.

In the first statement, there is an easily ambiguated idea that intelligence is part of the ant colonies. This could mean one of many possible things in common speech:
- The ants themselves are intelligent
- The ants are not intelligent, but the colony is well-organized and they act as an intelligent body together.

Both are likely (I'm not an ant specialist) wrong. The problem is that ordinary speech emphasizes the two above interpretations, and deemphasizes the intended one below of "emergence":

- The ants may not be intelligent, and the colony is probably not well-organized. However, the simplistic rules in the ant interactions create a complex system that behaves just like an intelligent body.

That's a lot of space to save by just saying that the colony shows emergent intelligence. A similar accent describes what happens with evolution and emergent traits. The word is intended to shift the focus from the idea that "the two lifeforms developed similar traits as a /direct/ consequence of such and such conditions" to the idea that "under such and such conditions, the two lifeforms happened to develop similar traits".

The system, in this case evolution, more properly describes the mechanism than the situation, in this case the habitat. The word emergent only brings to attention that fact.

Eliezer, although the comments did eventually get better, don't despair for the early comments on this post. Remember yourself, all you are finding in the comments is evidence confirming the belief that no one reading this blog is learning anything. I conjecture that those who have learned something just don't get excited enough to post because they don't disagree with you strongly enough or aren't sufficiently surprised to thank you publicly.

Of course, I still suspect, as you probably do, from years of experience that most readers of this blog believe they are learning to overcome bias when in fact they are just convincing themselves that they are learning to overcome bias because they have read about it and believe it's a virtue to overcome bias. And I don't exclude myself from this group either, because although I don't feel as though I'm thinking this way, that doesn't mean I might not secretly be and I will be revealed when I discover a serious error in my behavior and beliefs.

Thanks, Eliezer. Regarding your questions:

Is the property objective or subjective? The coarse grained property is objective -- e.g. the largest connected component in percolation. The meta-property that a coarse-grained property is emergent is as objective as the entropy of a configuration. It is model dependent, but in most cases we can't come up with a model that makes it go away.

To the extent "emergentness" is subjective, it is because it is relative to a model. So in some cases it could possibly be the result of ignorance of a better model. But we can't claim "emergentness" due to ignorance of any workable model, we can only say "I don't know".

Conjecturing that a property is emergent is a guide to inquiry. It is saying "Let's look for a model of this property that's robust under perturbation of the elements of the ensemble, but where the value of the property changes dramatically due to small changes in the average value of some properties of the elements. The model will be based on some highly simplified view of how the elements interact."

Some observations about models of emergent properties:

We don't have a very good "toolbox" for building them yet. We're getting better, but have a long way to go before we know how to proceed when we conjecture that a property is emergent.

We are even weaker in the design of emergent systems. That is why even very simple designs with emergent properties, like flocking, seem so striking. This is a serious disability because we depend on systems with major emergent properties, such as markets, and we don't know how to manage them very effectively.

Often when people claim properties are "mysterious", we could dispell these claims if we could respond with an intuitive account of how those properties emerge. Lacking such an account, we are often vulnerable to mystification.

I ll try a silly info-theoretic description of emergence:

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).

The particulars of the definition aren't even important. What's important is this is (or can be) a mathematical, rather than a scientific definition, something like the definition of derivative. Mathematical concepts seem more about description, representation, and modeling than about prediction, and falsifiability. Mathematical concepts may not increase our ability to predict directly, but they do indirectly as they form a part in larger scientific predictions. Derivatives don't predict anything themselves, but many physical laws are stated in terms of derivatives.

The concept of emergence is useful as a guard against certain errors, such as, for example, conspiratorial theories which explain phenomena as the product of intentions (malign or benevolent). Order does not always arise from intention. If society is lawful, that is not necessarily because there is some commander dictating that it be lawful. The lawfulness of society may be a phenomenon with a mostly dispersed, decentralized cause (e.g., lawfulness may be in large part enforced by ostracism of transgressors and thus enforced by all members of society rather than by an elite and privileged police apparatus applying the decisions of a legislature). Similarly, a sudden rise in the price of something may not be the product of a secret cartel or of a particular government policy or politician, but may be the result of a non-obvious confluence of disparate causes. When we say that prices emerge from the marketplace rather than being set by some authority, we are denying the idea that there is some person or group who has chosen that the price should be what it is, a person who can be appealed to to change his mind, or blamed for his decision.

Don't y'all find it a little suspicious that so many people think "emergence" is a useful concept, yet have different definitions of what it is? (Though more important is what it isn't.)

Next stage in the gauntlet: Why is this a useful concept? Why does it increase your understanding of the universe, and your predictive power? Can you force me to talk about emergence or a concept isomorphic to it?

"Tell me what it isn't!"

I'll go with TGGP's domain (video games), since that is what we blog about at Kill Ten Rats. The gaming blogosphere uses the term "emergent gameplay" more or less as TGGP defines it. Going back to my first online game, Asheron's Call, an example of what is not "emergent" gameplay is characters slaying monsters and leveling up. Monsters have the same code, but rarely win, so they rarely level; an example of emergent play was having characters sacrifice themselves to bunnies, who would gradually level up to a Night of the Lepus situation. Non-emergent was the use of "pyreals" (gold pieces) as currency; emergent was the economy that arose using alternate competing commodities as units of exchange.

As others have stated, I usually see "emergent" used as a shorthand for something like "the whole is not predictable from the parts." No cell in your brain understands Chinese, and neither does any part of Searle's Chinese room, but the system as a whole does. Is there a better term akin to the fallacy of composition or ecological fallacy?

I'm pretty ignorant on this, but I always thought that the phrase related to complex outcomes that result from surprisingly simple systems, so that the complexity is "emergent".

One example is chaos. One can have chaotic non-linear dynamic systems and non-chaotic non-linear dynamic systems.

But, again, I could have misunderstood.

There are a few examples of non-emergence. For example, if we tessellate many small equilateral triangles to create a larger equilateral triangle, the resulting figure will not show any emergent properties.

Outside of mathematics, though, the concept is vague and I can't see much use for it as applied to specific phenomena.

Aren't superconductivity and ferromagnetism perfect examples of emergent phenomena? I'm not saying that calling something an emergent phenomenon adds any deeper understanding of it. But I think there certainly are phenomena that can be fairly called as emergent.

Saying "X is emergent" is conveying some information, if there is someone in the room that does not already know this fact. Here is an example:

Quarks are emergent.

This is not an explanation though. It is more like a anti-explanation. I just claimed that there is an underlying explanation to quarks, and then stopped. I told you to make space for an explanation, in you mental world model, and then I left you with that space empty. If you believed my statement, and if you don't already know how quarks emerges and from what, I just made an explanation shaped hole in your mind. This is not nice of me.

But at least you now know that there is an explanation to be found. When you thought quarks was fundamental, you did not even know to look, because fundamental things can not be explained, only described.

Whilst I appreciate the validity of criticism offered here of the use of the word emergence (by itself) as if were an explanation sufficient unto itself - I think it a little harsh. To call it "futile" is almost acting as semantic stop sign itself for the term.

We need to take a little time to properly understand what is meant by emergence when used properly.

First that it is an observation rather than an explnation. But an observation with useful descriptive power since it observes that the phenomena under consideration is a process with properties whereby larger entities, patterns, and regularities arise through interactions among smaller or simpler entities that themselves do not exhibit such properties.

Therefore not at all properties that arise from interactions or combinations of smaller components are emergent (e.g. putting a whole bunch of magnets together just gives a larger magnetic field). So not all things arise are emergent.

So, while "emergence" is hardly an explanation - and one is obliged to look for the mechanisms that lead to the emergent behaviour - (such as how the polar hydrogen bonds in H20 give water surface tension - a property that a single H2O molecule does not exhibit) - nevertheless it's use as an observation has power since it points us to look for (and ask question about) how properties which do not exist in the sub components come to be via the interactions of the components (often multi-factor) - and also to see if there are simple factors or descriptive rules than have predictive power (e.g. flocking phenomena of birds)

I would suggest reading "More is Different", an excellent paper on the topic of emergent phenomena and the limits of reductionism. (http://www.ph.utexas.edu/~wktse/Welcome_files/More_Is_Different_Phil_Anderson.pdf).

The "More is Different" approach essentially notes that even when the basic bottom-up rules are known, they cannot be efficiently used to predict large-scale interactions. Those behaviours have to be studied as though they have their own set of rules (ie, the laws of chemistry), even though they emerge from a more fundamental set (the laws of physics). It seems to me that labelling a phenomena as "emergent" is a useful and descriptive term, which means "you need to study this phenomenon empirically to figure out its rules, because trying to make predictions based on fundamental principles won't get you anywhere".