torsdag 23. juli 2009

Ugo Bardi tolker Tainter



i "Peak Civilization": The Fall of the Roman Empire.

Litt overdramatisering av slakten i Teutoburgerskogen, synes jeg, men ellers veldig, veldig bra. Og langt. Et utdrag:


You'll probably agree that this explanation by Gibbon is a bit limited; just as are limited other interpretations by authors who came later. Spengler and Tonybee are two examples, but if we were to discuss their work in detail it would take - well - weeks; not hours. So, let me jump forward to the historian who - I think - has given a new and original interpretation of the decline of Rome: Joseph Tainter with his "The Collapse of Complex Societies". His book was published for the first time in 1990. [Jeg leste den som Påskekrim.]

It is a great book. I suggest to you to read it and ponder it. It is truly a mine of information about collapses. It doesn't deal just with the Roman Empire, but with many other civilizations. Tainter goes well beyond the simplistic interpretation of many earlier authors and identifies a key point in the question of collapse. Societies are complex entities; he understands that. And, hence, their collapse must be related to complexity. Here is an excerpt of Tainter's way of thinking. It is a transcription of a interview that Tainter gave in the film "Blind Spot" (2008)

In ancient societies that I studied, for example the Roman Empire, the great problem that they faced was when they would have to incur very high costs just to maintain the status quo. Invest very high amounts in solving problems that don't yield a net positive return, but instead simply allowed them to maintain what they already got. This decreases the net benefit of being a complex society.

Here is how Tainter describes his view in graphical form; in his book.



So, you see that Tainter has one thing very clear: complexity gives a benefit, but it is also a cost. This cost is related to energy, as he makes clear in his book. And in emphasizing complexity, Tainter gives us a good definition of what we intend for collapse. Very often people have been discussing the collapse of ancient societies without specifying what they meant for "collapse". For a while, there has been a school of thought that maintained that the Roman Empire had never really "collapsed". It had simply transformed itself into something else. But if you take collapse defined as "a rapid reduction of complexity" then you have a good definition and that's surely what happened to the Roman Empire.

So, what was important with the collapse of the Roman Empire is not whether or not there was an emperor in Rome (or, as it was the case later, in Ravenna). We might well imagine that the line of the emperors could have continued well after Romulus Augustulus - the last emperor. And even after him there remained a legitimate Roman Emperor in Byzantium, in the Eastern Empire. You could very well say that the Empire didn't disappear as long as there were emperors in Byzantium, that is, until Costantinople fell, in the 15th cenntury. And since the Russian Czars saw themselves as Roman emperors (that is where "Czar" comes from, from "Caesar"), you could say that the Roman Empire didn't disappear until the last Czar was deposed, in 1917. But that is not the point. The point is that the Roman Empire had started undergoing a catastrophic loss of complexity already during the third century. So, that was the real collapse. What happened later on is another story.

After that Tainter has spoken of complexity, and of the energy cost of complexity, it is perhaps surprising for us that he doesn't consider resource depletion as a cause of collapse. Resource depletion, after all, is the main theme of Jared Diamond's book "Collapse". It is how he interprets the collapse of many societies. Tainter explicitly denies that in his book. He says that if such a thing as depletion appears, then society should react against it. After all, it is normal: society always reacts to all kinds of crisis, and why shouldn't it react to resource depletion? This point made by Tainter may appear surprising - actually unpalatable - to people who have made resource depletion the centerpiece of their thought. Peak oilers, for instance.

The disagreement between peak oilers (and Diamond) and Tainter may not be so strong as it appears. That we'll see as we go deeper into the details. But before we do that, let me say something general about these explanations that people give for collapse. It happens all the time that people discover something that they describe as if it was the only cause for collapse. That is, they sort of get enamored of a single cause for collapse. They say, "I have the solution; it is this and nothing else."

Consider the story that Roman Empire collapse because the Romans used to drink wine in lead goblets; and so they died of lead poisoning. That has some truth: there is evidence of lead poisoning in ancient Roman skeletons; there are descriptions of lead poisoning in ancient Roman texts. Surely it was a problem, probably even a serious one. But you can't see this story of lead poisoning in isolation; otherwise you neglect everything else: the Roman Empire was not just people drinking wine in lead goblets. Think of a historian of the future who describes the fall of the American Empire as the result of Americans eating hamburgers. That would have some truth and for sure the kind of food that most Americans eat today is - well - we know that it is doing a lot of damage to the Americans in general. But you wouldn't say that hamburgers can be the cause of the fall of the American Empire. There is much more to that.

The same kind of reasoning holds for other "causes" that have been singled out for the fall of Rome. Think, for instance, of climatic change. Also here, there is evidence that the fall of the Roman Empire was accompanied by droughts. That may surely have been a problem for the Romans. But, again, we might fall in the same mistake of a future historian who might attribute the fall of the American Empire - say - to the hurricane Katrina.(I have nothing special against the American Empire, it is just that it is the current empire)

The point that Tainter makes, quite correctly, in his book is that it is hard to see the fall of such a complex thing as an empire as due to a single cause. A complex entity should fall in a complex manner, and I think it is correct. In Tainter's view, societies always face crisis and challenges of various kinds. The answer to these crisis and challenges is to build up structures - say, bureaucratic or military - in response. Each time a crisis is faced and solved, society finds itself with an extra layer of complexity. Now, Tainter says, as complexity increases, the benefit of this extra complexity starts going down - he calls it "the marginal benefit of complexity". That is because complexity has a cost - it costs energy to maintain complex systems. As you keep increasing complexity, this benefit become negative. The cost of complexity overtakes its benefit. At some moment, the burden of these complex structures is so great that the whole society crashes down - it is collapse.

I think that Tainter has understood a fundamental point, here. Societies adapt to changes. Indeed, one characteristic of complex systems is of adapting to changing external conditions. It is called "homeostasis" and I tend to see it as the defining characteristic of a complex system (as opposed to simply complicated). So, in general, when you deal with complex systems, you should not think in terms of "cause and effect" but, rather, in terms of "forcing and feedback". A forcing is something that comes from outside the system. A feedback is how the system reacts to a forcing, usually attaining some kind of homeostasis. Homeostasis, is a fundamental concept in system dynamics. Something acts on something else, but also that something else reacts. It is feedback. It may be positive (reinforcing) or negative (damping) and we speak of "feedback loops" which normally stabilize systems - within limits, of course.

Homeostasis has to be understood for what it is. It is not at all the same thing as "equilibrium" as it is defined in thermodynamics. For example, a human being is a complex system. When you are alive, you are in homeostasis. If you are in equilibrium, it means that you are dead. Homeostasis is a dynamical equilibrium of forces.

Also, homeostasis cannot contradict the principles of physics. It can only adapt to physical laws. Think of yourself swimming in the sea. Physics says that you should float, but you need to expend some energy to maintain a homeostatic condition in which your head stays above the water. Now, suppose that your feet get entangled with something heavy. Then, physics says that you should sink. Yet, you can expend more energy, swim harder, and still keep your head above the water - again it is homeostasis. But, if nothing changes, at some moment you'll run out of energy, you get tired and you can't keep homeostasis any more. At this point, physics takes over and you sink, and you drown. It is the typical behavior of complex systems. They can maintain homeostasis for a while, as long as they have resources to expend for this purpose.

Something similar occurs for human societies. When there is a forcing, say, an epidemics that kills a lot of people, societies react by generating more children. Look at the demographic statistics for our societies: there is a dip in numbers for the world wars, but it is rapidly compensated by more births afterward. Also in Roman times there were epidemics and the eruption of the Vesuvius that killed a lot of people. But those were small forcings that the Roman society could compensate.

Not all forcings can be compensated, but we know that the Romans were not destroyed by an asteroid that fell into the Mediterranean Sea. It might have happened, and in that case there would have been no feedback able to keep the empire together. We would have a single cause for the disappearance of the Roman Empire and everybody would agree on that. But that has not happened, of course. Perhaps, something like that has happened to the Cretan civilization; destroyed by a volcanic eruption - but that's another story.

So, in Tainter's view there is this feedback relationship between complexity and energy. At least the way I interpret it. Complexity feeds on energy and also strains the availability of energy. It is feedback. And not just energy; resources in general. So, I think that Tainter is right in refusing a simple explanation like "resource depletion is the cause of the fall of the Roman Empire". But, clearly, resources are an important part of his model. I think Tainter had in mind the Roman Empire when he developed this model, but it is of quite general validity. If this is the way things stand, his model is not in contrast with the models we have that see resource depletion as the main factor that causes collapse. But not the only cause. We must see collapse as something dynamic, and now I'll try to explain just that.


(Også noen veldig interessante kommentarer, spesielt en information dump fra arkeologen Boris ("mididoctors") om potteskår i Londinium: "they dumped them in the river"...)

Et viktig relatert poeng er at kapital må ansees som "kompleksitet" i Taintersk forstand (selv om det er diskutabelt om Tainter selv hadde det synet). Bardi var inne på dette tidligere i sommer, i The Fifth Problem: Peak Capital:

Here is a very clear description of how capital interacts with the other elements of the world model in a synopsis written in 1972 by the authors of the [Limits to Growth] report:

The industrial capital stock grows to a level that requires an enormous input of resources. In the very process of that growth it depletes a large fraction of the resource reserves available. As resource prices rise and mines are depleted, more and more capital must be used for obtaining resources, leaving less to be invested for future growth. Finally investment cannot keep up with depreciation, and the industrial base collapses, taking with it the service and agricultural systems, which have become dependent on industrial inputs.