Recognising Top-Down Causation
George Ellis, University of Cape Town
1: The Theme
A key assumption underlying most present day physical thought is the idea that causation is bottom up all the way: particle physics underlies nuclear physics, nuclear physics underlies atomic physics, atomic physics underlies chemistry, and so on. Thus all the higher level subjects are at least in principle reducible to particle physics, which is therefore the only fundamental science; as famously claimed by Dirac, chemistry is just an application of quantum physics .
However there are many topics that one cannot understand by assuming this one-way flow of causation. The flourishing subject of social neuroscience makes clear how social influences act down on individual brain structure ; studies in physiology demonstrate that downward causation is necessary in understanding the heart, where this form of causation can be represented as the influences of initial and boundary conditions on the solutions of the differential equations used to represent the lower level processes ; epigenetic studies demonstrate that biological development is crucially shaped by the environment .
What about physics? In this essay I will make the case that top-down causation is also prevalent in physics, even though this is not often recognised as such. This does not occur by violating physical laws; on the contrary, it occurs through the laws of physics, by setting constraints on lower level interactions. Thus my theme is that the foundational assumption that all causation is bottom up is wrong, even in the case of physics . Some writers on this topic prefer to refer to “contextual effects” or “whole-part constraints”. These are perfectly acceptable terms, but I will make the case that the stronger term “top-down causation” is appropriate in many cases.
George Francis Rayner Ellis is the Emeritus Distinguished Professor of Complex Systems in the Department of Mathematics and Applied Mathematics at the University of Cape Town in South Africa.
He co-authored The Large Scale Structure of Space-Time with University of Cambridge physicist Stephen Hawking, published in 1973, and is considered one of the world's leading theorists in cosmology. He is an active Quaker and in 2004 he won the Templeton Prize.
From 1989 to 1992 he served as President of the International Society on General Relativity and Gravitation. He is a past President of the International Society for Science and Religion. He is an A-rated researcher with the NRF.
Ellis attended the University of Cape Town, where he graduated with honors with a Bachelor of Science degree in physics with distinction. He received a PhD in applied mathematics and theoretical physics at Cambridge University.