Reductionism

There seems to be quite a misunderstanding about reductionism, based on a strong misapprehension of what it allows in physics [which is where the idea comes from, after all!]. I think it would be salutary for those wish to seriously get involved in the area to get to know a bit about what the modern-day physics view is. So I wish to draw your attention to the Nobel Prize lectures by the trio awarded the Physics Nobel Prize in 1998 for their discoveries relating to the Quantum Hall Effect. Specifically, here is the start of the Nobel lecture on Fractional Quantisation by Prof R B Laughlin [Nobel Laureate, Physics, 1998], as printed in Reviews of Modern Physics Vol 71, No 4, July (1999) 863-874:

"One of my favourite times in the academic year occurs in early spring when I give my class of extremely bright graduate students, who have mastered quantum mechanics but are otherwise unsuspecting and innocent, a take-home exam in which they are asked to deduce superfluidity from first principles. There is no doubt a very special place in hell being reserved for me at this very moment for this mean trick, for the task is impossible. Superfluidity, like the fractional Hall effect, is an emergent phenomenon - a low-energy collective effect of huge numbers of particles that cannot be deduced from the microscopic equations of motion in a rigorous way, and that disappears completely when the system is taken apart (see P Anderson, Science Vol 177, 393 1972.). .... The students feel betrayed and hurt by this experience because they have been trained to think in reductionist terms and thus to believe that everything that is not amenable to such thinking is unimportant. But nature is much more heartless than I am, and those students who stay in physics long enough to seriously confront the experimental record eventually come to understand that the reductionist idea is wrong a great deal of the time, and perhaps always. One common response in the early stages of learning is that superconductivity and the quantum Hall effect are not fundamental and therefore not worth taking seriously, When this happens I open up the American Institute of Physics handbook and show the disbeliever that the accepted values of the electric charge e and Planck's constant h are *defined* by these effects, and that ends that. The world is full of things for which one's understanding, i.e. one's ability to predict what will happen in an experiment, is degraded by taking the system apart, including most delightfully the standard model of elementary particles itself. I myself have come to suspect most of the important outstanding problems in physics are emergent in nature, including particularly quantum gravity."

The lecture continues to explain how one of the things emergent phenomena can do is create new physics, and particularly the quantum Hall effect (whereby cooperative phenomena create quasi-particles with fractional charge from interactions between particles with integral charge). It is true that some elementary particle physicists have perhaps not yet fully faced these issues - but the message from those seriously concerned with solid state physics (theory and experiment) is unambiguously clear.

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