So I think perhaps we are talking past each other. In particular, my definition of reductionism is that we can understand and model complex behavior by breaking a problem in to its constituent components and studying them in isolation. i.e. if you understand the micro-hamiltonian and the fundamental particles well, you understand everything. The idea of ‘emergence’ as physicists understand it (and as Laughlin was using it), is that there are aggregate behaviors that cannot be understood from looking at the individual constituents in isolation.
A weaker version of reductionism would say that to make absolutely accurate predictions to some arbitrary scale we MUST know the microphysics. Renormalization arguments ruin this version of reductionism.
In a sense this
if you wanted to know with 100% accuracy where the shell was going to land, you would have to go further down than this.
seems to be espousing this form of reductionism, which I strongly disagree with. There exist physical theories where knowing microphysics is irrelevant to arbitrarily accurate predictions. Perhaps it would be best to agree on definitions before we make points irrelevant to each other.
there are aggregate behaviors that cannot be understood from looking at the individual constituents in isolation
Can you give me an example of one of these behaviors? Perhaps my google-fu is weak (I have tried terms like “examples of top down causality”, “against reductionism”, “nonreductionist explanation of”), and indeed I have a hard time finding anything relevant at all, but I can’t find a single clearcut example of behavior which cannot be understood from looking at the individual constituents in isolation.
The fore-mentioned spontaneous symmetry breaking shows up in a wide variety of different systems. But, phase changes in general are probably good examples.
So I think perhaps we are talking past each other. In particular, my definition of reductionism is that we can understand and model complex behavior by breaking a problem in to its constituent components and studying them in isolation. i.e. if you understand the micro-hamiltonian and the fundamental particles well, you understand everything. The idea of ‘emergence’ as physicists understand it (and as Laughlin was using it), is that there are aggregate behaviors that cannot be understood from looking at the individual constituents in isolation.
A weaker version of reductionism would say that to make absolutely accurate predictions to some arbitrary scale we MUST know the microphysics. Renormalization arguments ruin this version of reductionism.
In a sense this
seems to be espousing this form of reductionism, which I strongly disagree with. There exist physical theories where knowing microphysics is irrelevant to arbitrarily accurate predictions. Perhaps it would be best to agree on definitions before we make points irrelevant to each other.
Can you give me an example of one of these behaviors? Perhaps my google-fu is weak (I have tried terms like “examples of top down causality”, “against reductionism”, “nonreductionist explanation of”), and indeed I have a hard time finding anything relevant at all, but I can’t find a single clearcut example of behavior which cannot be understood from looking at the individual constituents in isolation.
The fore-mentioned spontaneous symmetry breaking shows up in a wide variety of different systems. But, phase changes in general are probably good examples.