fevereiro 29, 2012

Tainter - The collapse of complex societies II

[I]ntensification in agriculture and resource production follows a pattern of declining marginal productivity [...] rationally-acting human populations will first exploit those resources that yield the best return per unit of effort, and still meet the needs of the population. If this is so, then it follows that any change in resource extraction must be in the direction of using resources that are more costly to obtain, process, distribute, and/or market, so that the marginal product of labor and other inputs declines. Thus, hunters and gatherers first exploit foods that are higher in nutritional value, and easier to obtain and process, than resources that are less favorable for these characteristics [...] In other spheres of resource extraction, minerals and energy forms can be ranked in terms of their ease of discovery, extraction, processing, and use. Resources that rank higher in these dimensions will be used before resources that don't, and when these are no longer sufficient, secondary resources will be employed. [...] Among whatever set of resources a population obtains, for whatever reasons, the law of diminishing returns is likely to apply. As demand for a commodity grows, increased production will at some point mean depletion or insuffciency of the least costly sources. At that point, more costly sources must be used, with declining marginal returns.

fevereiro 27, 2012

Tainter - The collapse of complex societies I

Despite a institutionalized authority structure, an ideological basis, and a monopoly of force, the rulers of states share at least one thing with chiefs and Big Men: the need to establish and constantly reinforce legitimacy. In complex as well as simpler societies, leadership activities and societal resources must be continuously devoted to this purpose. Hierarchy and complexity, as noted, are rare in human history, and where present require constant reinforcement. No societal leader is ever far from the need to validate position and policy, and no hierarchical society can be organized without explicit provision for this need.

Legitimacy is the belief of the populace and the elites that rule is proper and valid, that the political world is as it should be. It pertains to individual rulers, to decisions, to broad policies, to parties, and to entire forms of government. The support that members are willing to extend to a political system is essential for its survival. Decline in support will not necessarily lead to the fall of a regime, for to a certain extent coercion can replace commitment to ensure compliance. Coercion, though, is a costly, ineffective strategy which can never be completely or permanently successful. Even with coercion, decline in popular support below some critical minimum leads infallibly to political failure. Establishing moral validity is a less costly and more effective approach.

fevereiro 20, 2012


[...] There is however a less obvious, but far more important difference between nationalism and familial favoritism: Despite its mighty evolutionary basis, almost everyone recognizes moral strictures against familial favoritism. Almost everyone knows that “It would help my son” is not a good reason to commit murder, break someone’s arm, or steal. Indeed, almost everyone knows that “It would help my son” is not a good reason for even petty offenses – like judging a Tae Kwon Do tournament unfairly because your son’s a contestant.

Nationalism, in contrast, is widely seen as an acceptable excuse for horrific crimes against outgroups. Do you plan to murder hundreds of thousands of innocent foreign civilians? Just say, “It will save American [German/Japanese/Russian/whatever] lives” – and other members of your tribe will nod their heads. Do you want to deprive millions of foreigners of the basic human rights to sell their labor to willing buyers, rent apartments from willing landlords, and buy groceries from willing merchants? Just say, “It’s necessary to protect American jobs” in a self-righteous tone, then bask in the admiration of your fellow citizens - Bryan Caplan [via Café Hayek]

fevereiro 16, 2012

Falácia de Projecção Mental

Alfred North Whitehead no seu livro Process and Reality de 1929 apresentou o que ficou conhecido como The Fallacy of Misplaced Concreteness:
neglecting the degree of abstraction involved when an actual entity is considered merely so far as it exemplifies certain categories of thought (pg.11).
Este é um aviso sobre o erro de confundir o abstracto com o concreto. Esta ideia possui várias denominações. Talvez a mais conhecida seja a de Alfred Korzybski, 'O mapa não é o território'.

A este mesmo problema E.T. Jaynes designou por Falácia de Projecção Mental. No texto seguinte Jaynes usa-o para discutir as interpretações da teoria quântica e como a confusão entre estes dois níveis -- entre ontologia e epistemologia -- pode ter estado na origem do célebre desacordo de que deus não joga aos dados entre Einstein e Bohr:

The failure of quantum theorists to distinguish in calculations between several quite different meanings of 'probability', between expectation values and actual values, makes us do things that don't need to be done; and to fail to do things that do need to be done. We fail to distinguish in our verbiage between prediction and measurement. For example, the famous vague phrases: 'It is impossible to specify...'; or 'It is impossible to define...' can be interpreted equally well as statements about prediction or statements about measurement. Thus the demonstrably correct statement that the present formalism cannot predict something becomes perverted into the logically unjustified (and almost certainly false) claim that the experimentalist cannot measure it!

We routinely commit the Mind Projection Fallacy: supposing that creations of our own imagination are real properties of Nature, or that our own ignorance signifies some indecision on the part of Nature. It is then impossible to agree on the proper place of information in physics. This muddying up of the distinction between reality and our knowledge of reality is carried to the point where we find some otherwise rational physicists, on the basis of the Bell inequality experiments, asserting the objective reality of probabilities, while denying the objective reality of atoms! These sloppy habits of language have tricked us into mystical, pre-scientific standards of logic, and leave the meaning of any QM result ambiguous. Yet from decades of trial-and-error we have managed to learn how to calculate with enough art and tact so that we come out with the right numbers!

The main suggestion we wish to make is that how we look at basic probability theory has deep implications for the Bohr-Einstein positions. Only since 1988 has it appeared to the writer that we might be able finally to resolve these matters in the happiest way imaginable: a reconciliation of the views of Bohr and Einstein in which we can see that they were both right in the essentials, but just thinking on different levels.

Einstein's thinking is always on the ontological level traditional in physics; trying to describe the realities of Nature. Bohr's thinking is always on the epistemological level, describing not reality but only our information about reality. The peculiar flavor of his language arises from the absence of all words with any ontological import. J. C. Polkinghorne (1989, pp. 78,79) came independently to this same conclusion about the reason why physicists have such difficulty in reading Bohr. He quotes Bohr as saying:
"There is no quantum world. There is only an abstract quantum physical description. It is wrong to think that the task of physics is to find out how nature is. Physics concerns what we can say about nature."
[...] Bohr would chide both Wigner and Oppenheimer for asking ontological questions, which he held to be illegitimate. Those who, like Einstein (and, up until recently, the present writer) tried to read ontological meaning into Bohr's statements, were quite unable to comprehend his message. This applies not only to his critics but equally to his disciples, who undoubtedly embarrassed Bohr considerably by offering such ontological explanations as "Instantaneous quantum jumps are real physical events." or "The variable is created by the act of measurement.", or the remark of Pauli quoted above, which might be rendered loosely as "Not only are you and I ignorant of x and p; Nature herself does not know what they are."

We disagree strongly with one aspect of Bohr's quoted statement above; in our view, the existence of a real world that was not created in our imagination, and which continues to go about its business according to its own laws, independently of what humans think or do, is the primary experimental fact of all, without which there would be no point to physics or any other science.

The whole purpose of science is learn what that reality is and what its laws are. On the other hand, we can see in Bohr's statement a very important fact, not sufficiently appreciated by scientists today as a necessary part of that program to learn about reality. Any theory about reality can have no consequences testable by us unless it can also describe what humans can see and know. For example, special relativity theory implies that it is fundamentally impossible for us to have knowledge of any event that lies outside our past light cone. Although our ultimate goal is ontological, the process of achieving that goal necessarily involves the acquisition and processing of human information. This information processing aspect of science has not, in our view, been sufficiently stressed by scientists (including Einstein himself, although we do not think that he would have rejected the idea).

Although Bohr's whole way of thinking was very different from Einstein's, it does not follow that either was wrong. In the writer's present view, all of Einstein's thinking (in particular the EPR argument) remains valid today, when we take into account its ontological purpose and character. But today, when we are beginning to consider the role of information for science in general, it may be useful to note that we are finally taking a step in the epistemological direction that Bohr was trying to point out sixty years ago.

But our present QM formalism is not purely epistemological; it is a peculiar mixture describing in part realities of Nature, in part incomplete human information about Nature - all scrambled up by Heisenberg and Bohr into an omelette that nobody has seen how to unscramble. Yet we think that the unscrambling is a prerequisite for any further advance in basic physical theory. For, if we cannot separate the subjective and objective aspects of the formalism, we cannot know what we are talking about; it is just that simple. E.T. Jaynes, Probability in Quantum Theory (1996).

fevereiro 13, 2012


"[The Dis] wanted their civilization to last forever— that's the one thing we do know about them. They built for the ages in everything they did. The evidence is that they did last a very long time— maybe eighty million years. But early on, they discovered a disquieting truth we are only just learning ourselves. It is this: Sentience and toolmaking abilities are powerful ways for a species to move into a new ecological niche. But in the long run, sentient, toolmaking beings are never the fittest species for a given niche. What I mean is, if you need tools to survive, you're not well fitted to your environment. And if you no longer need to use tools, you'll eventually lose the capacity to create them. It doesn't matter how smart you are, or how well you plan: Over the longest of the long term, millions of years, species that have evolved to be comfortable in a particular environment will always win out. And by definition, a species that's well fitted to a given environment is one that doesn't need tools to survive in it.
"It's the same with consciousness. We know now that it evolves to enable a species to deal with unforeseen situations. By definition, anything we've mastered becomes instinctive. Walking is not something we have to consciously think about, right? Well, what about physics, chemistry, social engineering? If we have to think about them, we haven't mastered them— they are still troublesome to us. A species that succeeds in really mastering something like physics has no more need to be conscious of it. Quantum mechanics becomes an instinct, the way ballistics already is for us. Originally, we must have had to put a lot of thought into throwing things like rocks or spears. We eventually evolved to be able to throw without thinking— and that is a sign of things to come. Some day, we'll become like the people of Dis, able to maintain a technological infrastructure without needing to think about it. Without needing to think, at all…
"The builders of Dis faced a dilemma: The best way to survive in the long run on any world they colonized was to adapt yourself to the environment. The best survivors would be those who no longer needed technology to get by. They tried to outlaw such alterations, but how do you do such a thing for the long term without suppressing the scientific knowledge that makes it possible? Over tens or thousands of millennia, you can only do this by suppressing all technological development, because technologies intertwine. This tactic results in the same spiral into nontechnological life. So inevitably, subspecies appeared that were better survivors in a given locale, because they didn't need technology in that locale. This happened every time, on all their worlds.
"The inhabitants of Dis had studied previous starfaring species. The records are hard to decipher, but I found evidence that all previous galactic civilizations had succumbed to the same internal contradictions. The Dis-builders tried to avoid their fate, but over the ages they were replaced on all their worlds by fitter offspring. These descendents had no need for tools, for culture, for historical records. They and their environment were one. The conscious, spacefaring species could always come back and take over easily from them. But given enough time… and time always passes… the same end result would occur. They would be replaced again. And so they saw that their very strength, the highest attainments they as a species had achieved, contained the seeds of their downfall.
"This discovery finally explained to us why toolmaking species are rare to begin with. It takes an unusual combination of factors to create a species that is fit enough to survive, but at the same time is so unfit in its native environment that it must turn to its weakest organ, its brain, for help. Reliance on tools is a tremendous handicap for any species; only a few manage to turn it into an asset.
"The builders of Dis knew they were doomed. We all are: technological civilization represents a species' desperate attempt to build a bubble to keep hostile environments at bay. Sentient species also never cooperate with one another over the long term, because the environments they need in order to live are incompatible. Some, like the Chicxulub, accept this easily and try to exterminate everyone else. Even they can't stop their own evolution and so eventually they cease to be starfaring species. Destruction or devolution are the only choices."
Karl Schroeder - Permanence

fevereiro 06, 2012

Perfeito, Imperfeito

O teorema de Bayes mostra como se deve integrar nova evidência ao conhecimento prévio já adquirido. A sua aplicação determina exactamente como a inferência e a aprendizagem podem ser optimizadas. Porém, não é assim que a cognição humana funciona. Para entender esta são necessários modelos de inferência imperfeitos, complexos, prevendo decisões que possam ser sub-óptimas, até incoerentes (e.g., a Prospect Theory de Daniel Kahneman). Este é um reflexo da história evolutiva do nosso cérebro que, como tudo o resto na evolução, é o possível entre as limitações físicas e cognitivas, o contigente da geografia, do clima e do tempo onde a nossa espécie se desenvolveu, dos compromissos cegos do passado.

fevereiro 02, 2012


As palavras representam um compromisso de significados. Cada imagem do mundo, cada pessoa, encontra na linguagem uma tradução comum, uma comunicação privilegiada com os outros. Mas esta tradução tem falhas, desacordos que passam sem ser anunciados sendo, com suficiente azar, fontes de tragédia. A maioria das palavras não aparentam ter este problema, como 'formiga', 'unha', 'amarelo'. Infelizmente, porque decerto não é coincidência, palavras com impacto social, como 'política', 'igualdade' ou 'juramento', são riquíssimas em equívocos. Veja-se esta última, 'juramento'. Detenho dois significados distintos desta palavra: (i) o intuito de respeitar a promessa feita independentemente do contexto, ou (ii) o intuito de respeitar a promessa só enquanto os pressupostos iniciais continuem a ser respeitados. A distância entre estas duas interpretações é a distância que separa, por exemplo, um energúmeno com farda de um polícia.