janeiro 31, 2014

Unwelt II

"In 1909, the biologist Jakob von Uexküll introduced the concept of the umwelt. He wanted a word to express a simple (but often overlooked) observation: different animals in the same ecosystem pick up on different environmental signals. In the blind and deaf world of the tick, the important signals are temperature and the odor of butyric acid. For the black ghost knifefish, it's electrical fields. For the echolocating bat, it's air-compression waves. The small subset of the world that an animal is able to detect is its umwelt. The bigger reality, whatever that might mean, is called the umgebung. The interesting part is that each organism presumably assumes its umwelt to be the entire objective reality "out there." Why would any of us stop to think that there is more beyond what we can sense?" David M. Eagleman

janeiro 17, 2014

A impossibilidade do realismo

"What we would all like [...] is an understanding of the fundamental processes that govern the Universe, an understanding that is not just useful for calculation but an understanding that is true in some deeper sense. Typically, a scientist sees the latter point as either obvious and important, or else completely irrelevant. I would like to argue that we don’t have a choice; there is some very clear sense in which truth is not what is returned by any finite scientific investigation; all that is returned is plausibilities (some of which become very very high), and those plausibilities relate not directly to the truth of the hypotheses in question, but rather to their use or value in describing the data. 

The fundamental reason scientific investigations can’t obtain literal truth is that no scientific investigator ever has an exhaustive (and mutually exclusive) set of hypotheses. Plausibility calculations are calculations of measure in some space, which for our purposes we can take to be the space formed by the union of every possible set of scientific hypotheses, with their parameters and adjustments set to every possible set of values." -- David Hogg, Is cosmology just a plausibility argument?.

janeiro 15, 2014

Reductionism

[...] reductionism is not so much a positive hypothesis, as the absence of belief—in particular, disbelief in a form of the Mind Projection Fallacy. [...] we use entirely different models to understand the aerodynamics of a 747 and a collision between gold nuclei in the Relativistic Heavy Ion Collider.  A computer modeling the aerodynamics of a 747 may not contain a single token, a single bit of RAM, that represents a quark. So is the 747 made of something other than quarks?  No, you're just modeling it with representational elements that do not have a one-to-one correspondence with the quarks of the 747.  The map is not the territory. [...] As the saying goes, "The map is not the territory, but you can't fold up the territory and put it in your glove compartment."  Sometimes you need a smaller map to fit in a more cramped glove compartment—but this does not change the territory.  The scale of a map is not a fact about the territory, it's a fact about the map.

[...]

To build a fully accurate model of the 747, it is not necessary, in principle, for the model to contain explicit descriptions of things like airflow and lift.  There does not have to be a single token, a single bit of RAM, that corresponds to the position of the wings.  It is possible, in principle, to build an accurate model of the 747 that makes no mention of anything except elementary particle fields and fundamental forces.
"What?" cries the antireductionist.  "Are you telling me the 747 doesn't really have wings?  I can see the wings right there!"
The notion here is a subtle one.  It's not just the notion that an object can have different descriptions at different levels.
It's the notion that "having different descriptions at different levels" is itself something you say that belongs in the realm of Talking About Maps, not the realm of Talking About Territory.

It's not that the airplane itself, the laws of physics themselves, use different descriptions at different levels—as yonder artillery gunner thought.  Rather we, for our convenience, use different simplified models at different levels.

[...]

So when your mind simultaneously believes explicit descriptions of many different levels, and believes explicit rules for transiting between levels, as part of an efficient combined model, it feels like you are seeing a system that is made of different level descriptions and their rules for interaction.

But this is just the brain trying to be efficiently compress an object that it cannot remotely begin to model on a fundamental level.  The airplane is too large.  Even a hydrogen atom would be too large.  Quark-to-quark interactions are insanely intractable.  You can't handle the truth.

But the way physics really works, as far as we can tell, is that there is only the most basic level—the elementary particle fields and fundamental forces.  You can't handle the raw truth, but reality can handle it without the slightest simplification.  (I wish I knew where Reality got its computing power.)

The laws of physics do not contain distinct additional causal entities that correspond to lift or airplane wings, the way that the mind of an engineer contains distinct additional cognitive entities that correspond to lift or airplane wings.

This, as I see it, is the thesis of reductionism.  Reductionism is not a positive belief, but rather, a disbelief that the higher levels of simplified multilevel models are out there in the territory.  Understanding this on a gut level dissolves the question of "How can you say the airplane doesn't really have wings, when I can see the wings right there?"  The critical words are really and see." -- Yudkowsky (http://lesswrong.com/lw/on/reductionism/)

DanielLC reply to another comment: "One minor quibble; how do we know there is any most basic level?". Levels are an attribute of the map. The territory only has one level. Its only level is the most basic one. Let's consider a fractal. The Mandelbrot set can be made by taking the union of infinitely many iterations. You could think of each additional iteration as a better map. That being said, either a point is in the Mandelbrot set or it is not. The set itself only has one level.