Thursday, August 25, 2022

Is There Causation in Fundamental Physics?

Emily Adlam tries to justify quantum causation in a new paper:
Bertrand Russell famously argued that causation plays no role in science: it is ‘a relic of a bygone age, surviv- ing, like the monarchy, only because it is erroneously supposed to do no harm.’ [1] Cartwright [2] and later writers moderated this conclusion somewhat, and it is now largely accepted that in a macroscopic setting causal concepts are an important part of the assessments we make about possible strategies for action.

But the view that causation in the usual sense of the term is not present in fundamental physics, or at least that not all fundamental physical processes are causal, remains prevalent [3, 4] - for example, Norton writes that ‘(causes and causal principles) are heuristi- cally useful notions, licensed by our best sciences, but we should not mistake them for the fundamental principles of nature’ [5].

Furthermore, many influential philosophical analyses of causation posit that causation arises only at a macroscopic level, as a result of the thermodynamic gradient [6,7], interventions [8,9], the perspectives of agents [10], or some such feature of reality which plays no role in fundamental physics.

In light of this widespread orthodoxy, it may seem surprising that in recent years a significant literature around causation has sprung up within quantum foundations.

[1] Bertrand Russell. On the notion of cause. Proceedings of the Aristotelian Society, 13:1–26, 1912.
[2] Nancy Cartwright. Causal laws and effective strategies. No╦ćus, 13(4):419–437, 1979.

The opinion against causation is so bizarre that it is hard for me to understand it. In my view, causation is fundamedental at all levels of science. Events are influenced by events in the backwards light cone, and science is all about explaining that.

How can philosophers be so against causation?

I see different arguments.

If time travel into the past is possible, then it is hard to see what causation means.

If you use a Lagrangian formulation of physics, then you often find a solution for all times at once, as opposed to strictly deducing future events from past events. However there is usually another formulation where the past causes the future.

Russell's argument was in 1912, before quantum mechanics. He seemed to think that there were universal mathematical laws determining the future. In his view, that was not really causation, like a human causing something to happen.

Quantum uncertainties lead to other questions. Some people seem to think that probabilities cannot be caused, but that is plainly untrue, in the ordinary English language usage. People say that smoking causes lung cancer, even thought the connection is probabilistic.

Some say that causality cannot explain the Bell correlations:

note that the proof of the Bell inequality can be regarded as telling us that any causal model for correlations violating the Bell inequality must postulate a causal connection between the choice of measurement on one particle and the outcome of the measurement on the other particle, but the quantum mechanical no-signalling theorem ensures that at the statistical level there will be no dependence of the outcome on the measurement choice, so if we wish to represent these statistics by a causal model we must carefully ‘fine-tune’ the parameters of the model to ensure that the underlying causal influences exactly cancel out so as to be invisible at the level of the empirical statistics.
I think that the problem here is that if you think that Bell proved nonlocality, and if causation is a local mechanism, then there is a problem.

But Bell did not prove nonlocality. Quantum mechanics is a local theory, consistent with causation. Many people misunderstand this.

1 comment:

  1. The idea that causation is not necessary is pretty ridiculous, especially from a philosophical perspective. If you believe in arithmetic or logic, you must also believe in causation. There is no sequence possible without it, there are no order of operations without it, there can be no computation or calculation of any kind without it. Even precious probabilities are NOTHING BUT calculations, and they certainly don't calculate themselves spontaneously or have existence independent of the data they were calculated from.

    There is no timeless anything except in make-believe, euphemism, or fantasy...and every single fantasy ever entertained takes some time in which to occur.