Friday, 5 August 2011

More is Different

In this blog post I will present the central ideas (as I see them) contained within a paper authored by P. W. Anderson: More is different - broken symmetry and the nature of the hierarchical nature of science.

At the heart of this paper is an argument for the legitimacy and importance of interdisciplinary science. Anderson argues his case by demonstrating (with examples) how reductionism breaks down, and that what is often needed to explain many phenomenon is an appreciation of the importance of emergent properties.
The main fallacy in this kind of thinking is that the reductionist hypothesis does not by any means imply a "constructionist" one: The ability to reduce everything to simple fundamental laws does not imply the ability to start from those laws and reconstruct the universe. ...

The constructionist hypothesis breaks down when confronted with the twin difficulties of scale and complexity. The behaviour of large and complex aggregates of elementary particles, it turns out, is not to be understood in terms of a simple extrapolation of the properties of a few particles. Instead, at each level of complexity entirely new properties appear...

Anderson argues that interdisciplinary sciences offer perhaps the best vantage point from which to develop new conceptual frameworks based on overlooked patterns of behaviour.
... it is not true, as a recent article would have it, that we each should "cultivate our own valley, and not attempt to build roads over the mountain ranges... between the sciences." Rather, we should recognize that such roads, while often the quickest shortcut to another part of our own science, are not visible from the viewpoint of one science alone.

... we have yet to recover from that of some molecular biologists, who seem determined to try to reduce everything about the human organism to "only" chemistry, and all mental disease to the religious instinct. Surely there are more levels of organization between human ethology and DNA than there are between DNA and quantum electrodynamics, and each level can require a whole new conceptual structure.
I find Anderson's argument very persuasive and pertinent and highly recommend reading the paper in full!

Martin

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