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How to know whether A and B is causal or correlated? Is it correct to say that physicists have always been concerned about causation? The laws of physics are stated in terms of equations that have nothing to say about causation. They are correlational laws.

Please give me some reference if possible.

Geoffrey Thomas
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quanity
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  • Please precise the difference. In general, causality is correlation (two related events), and the understanding of arithmetic equations (qualified by you as correlations: F(x) is related with 2x on the arithmetic statement F(x)=2x) depend on causality (F(x)=2x implies that if x is the cause, the consequence is 2x). In some contexts, it is considered that an equation is causal if its parts are correlated. – RodolfoAP Aug 07 '22 at 16:43
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    We observe a correlation but a cause in general is accounted for in the context of a theory. – Mauro ALLEGRANZA Aug 07 '22 at 17:44
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    It helps if there's a story. Every time I flip the light switch the light comes on. Is that just a correlation? Well, there's a compelling story that says that flipping the light switch closes a circuit between the lamp and the power company. I believe it. So it's causation. Now why do I believe that story? I've never personally been to the power plant, nor personally traced the wiring between my room and the power plant. I haven't personally investigated the theory of electricity. So it comes down to epistemology. How do I know what I think I know? What stories do I believe? – user4894 Aug 07 '22 at 19:08
  • @Mr.White It is the task of the community, not moderators, to handle simple things like closure for being a duplicate. Moderators should, ideally, only intervene where the moderation privileges of members end and intervention is still needed. – Philip Klöcking Aug 07 '22 at 19:10
  • One does not need a microscope to see that things are not running so ideally at this place. It might be a time to moderate some more. –  Aug 07 '22 at 19:13
  • @Mr.White Feel free to do so yourself and raise this on our Meta site. If you look not too hard there, you will find quite a lot of nuanced discussions about the appropriate amount of moderator intervention. – Philip Klöcking Aug 07 '22 at 19:17
  • Simple example of the Granger-causality test for statistical causal significance here, in the [Relationship between silver and gold prices historically](https://money.stackexchange.com/a/90988/11768) - with plenty of links to literature. – Chris Degnen Aug 07 '22 at 20:49
  • @Mr.White: I think what you are observing is that Stack Overflow is *wildly* busier than this site. – CriglCragl Aug 08 '22 at 20:54
  • @quanity Your revised question seems more like a question for [hsm.se]. – wizzwizz4 Aug 13 '22 at 13:08
  • See 'Is the idea of a causal chain physical (or even scientific)?' https://philosophy.stackexchange.com/questions/70930/is-the-idea-of-a-causal-chain-physical-or-even-scientific/72055#72055 Causation is a kind of narrative structuring, where we pick out key events towards abstraction transferable knowledge, & understsnding past future & counterfactual events – CriglCragl Sep 21 '22 at 12:36

2 Answers2

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Physics is concerned with causality in the framework of natural law. Causality there is deeply embedded in both the two main fundamental theories: QM & GR. In QM, because time is open and things happen whilst in GR, its proveable that the very structure of spacetime is causal. This is a theorem of Malament who showed that a spacetime could be rebuilt (upto a conformal factor) from a knowledge of its causal structure. This has prompted the development of the causal set programme in Quantum Gravity.

More broadly speaking, as al-Ghazali pointed out, physics is merely correlational, requiring the intervention of the Absolutely Real to make what is wholly unreal, real. But this is outside what is now understood to be physics - if not what was understood traditionally as metaphysics. Of course some physicalists take physics to be the ground but this is not primarily because they are physicists or even interested in physics but because they are a certain tribe of materialists.

Mozibur Ullah
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Causation in physics goes like this:

  • We have some equations that describe how the state of a system changes over time. These equations typically give the time-derivative of different variables of the system, as a function of the current values of those variables.
  • At time t, we set up some initial conditions for the system.
  • We use the equations of the system to trace how the system changes, based on its initial conditions, to some later conditions at a later time.
  • Then we say that the initial conditions caused the later conditions.

It is true that the equations typically don't inherently say which is the cause and which is the effect, and in this sense you might say they are describing mere correlation. We might use the same equations to trace how the state of the system changes backwards in time. However, by convention, the positive time direction is considered the direction of causation.

Here's another way you can use the equations to talk about causation:

  • You first deduce that initial conditions X at time t lead to later conditions Y at time t2 > t, according to the equations of the system
  • You change the initial conditions, so that instead of X you have X2, slightly different from X. Then you trace from X2 at time t, to later conditions Y2 at time t2 > t.
  • Then you say that the change in initial conditions from X to X2, caused a change in later conditions from Y to Y2. This lets us talk about "but-for" causation: what would have happened, if initial conditions had been different.
causative
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  • -1: Actually, Newton used "causal" language is his *Principia*. For example he said "a particle *perseveres* in rectilinear motion or at rest". This language was taken out of the *Principia* by a certain tribe of French mathematical materialists as it offended their notion of what was proper to nature and this has fed into how physics is taught and mathematicians think about physics but not how physicists think about physics. For example take Sorkins "Causal Sets" as a fundamental theory of physics. Notice the word 'Causal' in the name of the theory ... – Mozibur Ullah Sep 20 '22 at 00:11
  • @MoziburUllah You are speaking as if I had said there was something wrong with causal language in physics. I don't think I said anything to that effect. I mean, look at my user name. – causative Sep 20 '22 at 00:16
  • Really? You say, "it is true that the equations typically don't inherently say which is the cause and which is the effect, and in this sense you might say they are describing correlation ...". This is why physicists invented the science of thermodynamics to explain why time goes forwards only. – Mozibur Ullah Sep 20 '22 at 00:21
  • @MoziburUllah Yes, in *that* sense you might say they are describing correlation, and then I go on to describe a *different* sense in which you might say they are describing causation: "However, by convention, the positive time direction is considered the direction of causation." Furthermore the bullet points, which you must not have read, are entirely about when we can say something caused something else. – causative Sep 20 '22 at 00:23
  • No. It's not correlation. It's causal. Why would physicists bother inventing thermodynamics if they didn't think there was a direction to time. You ate confusing physics with mathematics. Mathematics is acausal. – Mozibur Ullah Sep 20 '22 at 00:27
  • @MoziburUllah Correlation and causation are not mutually exclusive. To establish causation, statistically we must first show correlation and then go a step further. Causation is a type of correlation. See Judea Pearl's book, "causality." – causative Sep 20 '22 at 00:50
  • Newtons laws as written by Newton are **not** correlative - they are **causative**. Einstein himself wasn't too fond of the geometrisation of physics as so many physicists seem to think physics is - he saw GR as the unification of inertia with mass - part of his Machian programme. This has led to many odd ideas about GR as though it is a block universe theory when one British physicist has shown that its an aspect of **local becoming**. You can't have local becoming without **local causality**. – Mozibur Ullah Sep 20 '22 at 00:54