More is Different, Anderson

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Q_Goest
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In Phil Anderson’s often quoted paper “More is Different”, he claims, “The elementary entities of science X obey the laws of science Y.” The first page of his paper outlines what he wants here by providing an abbreviated table indicating a type of scientific ladder which starts at the lowest possible level of elementary particle physics and advancing to the social sciences.

Anderson goes on to say:
But this hierarchy does not imply that science X is “just applied Y.” At each stage entirely new laws, concepts, and generalizations are necessary, requiring inspiration and creativity to just as great a degree as the previous one. Psychology is not applied biology, nor is biology applied chemistry.
He uses the phrase “entirely new laws” to describe each stage, seemingly to indicate that new physical laws are required at each stage, which leads me to the question of this post.

What do you think Anderson means by this phrase?

I can think of a few specific meanings:
1. At one extreme, he could be truly saying that new physical laws are necessary at each level which would indicate that perhaps we don’t yet know what these laws are.
2. At the other extreme, he may be merely referring to the generalities created by people in various fields such as the law of supply and demand which are general concepts that don’t require new physical laws, but only general laws which are created by people and are not natural, physical laws.
3. He could be saying something in between, such that the laws we already understand (ex: supply and demand) are actually physical laws in the sense that they have causal affects over the sub-levels.
4. Or perhaps he means something else.

Note that right after he makes the above statement he also says.
Before beginning this I wish to sort out two possible sources of misunderstanding. First, when I speak of scale change causing fundamental change I do not mean the rather well-understood idea that phenomena at a new scale may obey actually different fundamental laws – …
This seems to indicate #2 above, but I don’t want to make that assumption just yet.

So what do you think Anderson means here?
 

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  • #2
D H
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All of the above.

In some cases, those new physical laws developed by changing levels of abstration are absolutely necessary. The many intervening layers of abstraction between root-level physics and evolutionary biology militate against reasoning about evolutionary outcomes in complex biological systems on the basis of physical laws. Relating the theory of evolution to the most basic concepts in physics (e.g., gravity, conservation of energy, the Pauli exclusion principle) would be an incredibly difficult task.

In other cases, those new physical laws are mere conveniences. Conservation of energy is expressed in many different ways even within the realm of physics, such as conservation of mass, the vis-viva equation in orbital mechanics, the first law of thermodynamics, and the Reynolds transport theorem in fluid mechanics.

Reasoning from first principles is a nice thing, but doing so often gets in the way of doing the work at hand.
 
  • #3
Q_Goest
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Hi DH,
I don’t disagree the constructionist hypothesis breaks down when trying to explain psychology or evolution in terms of chemistry or biology, but honestly I don’t see any constructionists in the world today trying to do such things. As he says, it’s just to complicated. I have no problem with that. I don’t think anyone does.

What gives you the impression from reading this paper (or anything from Anderson) that Anderson believes that social science for example, needs new physical laws based on psychology which is based on physiology? (Other than the table he provides on the first page of course.) He offers no examples of potential physical laws above the level of many-body physics. What in his writing gives you the impression he thinks that new physical laws of nature are necessary at each level? When I read this sentence in context:
At each stage entirely new laws, concepts, and generalizations are necessary, requiring inspiration and creativity to just as great a degree as the previous one.
I see him saying "entirely new concepts" and entirely new generalizations, which to me indicates the laws he’s refering to are concepts and generalizations, not actual new physical laws. He says they require inspiration and creativity to just as great a degree as the previous level, so the phrase "entirely new laws" seems a bit out of place here if we are to assume he means “natural, physical laws”. It doesn't say "entirely new laws of nature" or “fundamental laws” which would have been easy enough to write had he meant that. He puts in this sentence the word 'concept' and 'generalizations' alongside the word 'law' and then seems to back away from saying these are new physical laws that he's referring to by immediately going into what he doesn't mean:
I do not mean the rather well-understood idea that phenomena at a new scale may obey actually different fundamental laws
 
  • #4
Q_Goest
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Interesting… take a look at “Simple Lessons from Complexity” by Goldenfeld and Kadanoff. Science, 2 Apr. ‘99
http://jfi.uchicago.edu/~leop/SciencePapers/simplelessons.pdf

He opens up with:

One of the most striking aspects of physics is the simplicity of its laws. Maxwell’s equations, Schrodinger’s equation, and Hamiltonian mechanics can each be expressed in a few lines. The ideas that form the foundation of our worldview are also very simple indeed: The world is lawful, and the same basic laws hold everywhere.
This goes along with what Anderson says:

I think it will be accepted that all ordinary matter obeys simple electrodynamics and quantum theory, and that really covers most of what I shall discuss. (As I said, we must all start with reductionism, which I fully accept.)
Goldenfeld also discusses conservation of energy, as DH mentions. He explains that there are three basic concepts that are fundamental to nature, locality, conservation and symmetry, while explaining their applicability to fluid dynamics as an example. Clearly, Goldenfeld is speaking from the viewpoint that no new physical laws need to be addressed to higher level phenomena.

At the end, he quotes Anderson’s paper directly, seemingly in agreement to his own.

Thoughts? Still looking for additional references.
 

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