September 9, 2012, by Stephen Mumford

Metaphysics and Better Physics

Last week I attended a workshop on Causation in Physics, part of a larger project called Causation in Science (CauSci for short). Among the speakers was the ever-eloquent and erudite Thor Sandmel whose talk raised the question of how physics relates to our experience of causation in the world. We have a philosophical theory of what it is for one thing to cause another but is it superseded by the claims of physics?

I recalled again Bertrand Russell’s old attack on the philosophical approach in his famous 1913 paper ‘On the Notion of Cause’. Our regular pre-theoretical understanding of the world has it that causing involves an asymmetry. Causes produce their effects rather than vice versa. An impact from a brick makes a window smash, for instance: it is not the smashing of the glass causing the brick to hit it. And light shining on a plant causes it to grow; the plant’s growth doesn’t make the sun shine. But Russell noted that physics had eliminated the asymmetry that was essential to this popular conception of cause. Instead, the language of physics was a language of equations (F=ma, F=Gm1m2/d2, and so on). And the thing about equations is that they can be read either way: from left to right or from right to left. In other words, physics described a world in which all was symmetrical and, while we were used to processes that ran from A to B, in theory they could just as well run from B to A. So much for causation.


Russell was perhaps the first in a long line of scientifically informed philosophers to suggest that philosophy had best leave the description of reality to science. Where metaphysics and physics came into conflict, we should always give way to the physicists. They were the experts. And physicists have themselves been happy to join in this attempted erosion of philosophy’s domain. Stephen Hawking, Lawrence Krauss, and even our beloved Professor Brian Cox have all recently proclaimed the end of philosophy or questioned whether it says anything useful at all.

During Sandmel’s stimulating talk, however, for the first time I realised that there was no reason at all why a metaphysician should run scared from Russell’s attack. Much of physics consists in the construction of a mathematical model of reality. But the world is not a number: not a function, nor an equation. Physics is an attempt to describe reality in largely mathematical terms but we should not mistake the description for the reality. Mathematics provides a structure and there must be something concrete in which it is realised, otherwise we are living as a collection of mere abstract entities. If there is a clash between our philosophical grasp of the world and its description in physics it doesn’t automatically follow that the philosophers should roll over for physics and submit meekly to its authority. Where the mathematical modelling of physics fails to account for a core experience and conception we have of the world, sometimes we should demand a better physics.

Russell’s interpretation of physics can of course be contested. Even where an equation adequately describes some real situation, intervention to change one value (and thereby the others) remains a possibility. That looks like asymmetry – and intervention sounds like causation. It is worth noting further that the truths of cutting-edge physics can be just as debated and speculative as any in philosophy. There are already well-known attempts to reintroduce asymmetry back into the field: in information theory and with the notion of entropy, for instance.

Philosophy doesn’t provide everything we need to describe the world. We also need the evidence of our senses. But philosophy has a role. A complete understanding would include both of the facts of experience and the general sort of metaphysical thinking provided by the philosopher, for there are some questions that unaided science simply cannot answer.


For an introduction to metaphysics, see here: shameless plug

For more on Russell’s own metaphysics, see here: and again!

Posted in MetaphysicsPhilosophy