Thinking About Causality (Part 1)

Starting at the end of a book is typically a bad idea, but in this case I think it’s enlightening to begin at the end, as it were. For one, Pearl makes some of his most dramatic claims and I want to draw attention to those claims and treat them as promissory notes to be cashed in by the final substantive chapter. I also want to ensure that these claims are capable of holding up to philosophical scrutiny.

My (newest) position concerning causality is one that I’m fairly confident Pearl shares, which is good because, for one, it’s an unpopular position and, two, it’s always nice to have friends. Lately, I’ve been entertaining the notion of an “epistemic” conception of causality, which means that causation need not be thought of so much as a feature of the world but as a feature of the way we interpret the world. These are very different interpretations of causation since one implies that causal relations are things in the world (whether we observe them or not) and the other implies that causal relations are items of our understanding of the world (which may not be there if we’re not here to observe them). I think Pearl holds this position and I’ll give you some reasons to back up my claim.

First, when discussing the problem Bertrand Russell has regarding the problem of causation, Pearl is quick to point out that the asymmetry of causal hypotheses is not due to the structure of the universe as such, but is instead due to the ways in which researchers go about studying some small part of any physical system. Pearl says:

The lesson is that it is the way we carve up the universe that determines the directionality we associate with cause and effect. Such carving is tacitly assumed in every scientific investigation (p.420).

Now, while not a definitive acceptance of this epistemic conception of causality, it is still telling, I think. Pearl is responding to Russell’s criticism that in advanced physics causal language never comes up by arguing that the language of causality only comes into the picture when researchers focus on areas of the physical universe that are not maximally inclusive. In other words, it is only in isolated subsystems that causality appears: take a subset of the interrelations between physical objects and you will find causal relations; take the system as a whole and those causal relations disappear and the system seems symmetric.

There is something very interesting going on here with the related notions of “boundary conditions,” “input/output relations,” and “background conditions.” When we first isolate some subsystem and then characterize it in terms of inputs and outputs we draw a boundary around some phenomenon and, in so doing, create this asymmetry between what was designated as the input and the output. This idea is worth exploring further and, I’m sure, will become a much-debated item of discussion on this blog. It’s also in my dissertation, so there’s that.

Now, to be fair to the realist and a possible realist-reading of Pearl, declaring something to be an input does not mean that one must be an anti-realist regarding the nature of that element (inputs can be just as real as anything, after all). Now whether Pearl is or is not a realist about causation is going to be one topic of this multi-part discussion, but I am going to try to defend this rather extreme position I’ve outlined above and argue that, in fact, it is the labeling of certain phenomena as “input/output relations” that provides the directionality and the asymmetry of our causal hypotheses about those phenomena. So I agree with Pearl when he says that it is the act of investigation of an aspect of the universe that brings about causal language and I’m going to take him literally and defend the position that causation is just that; namely, the way in which we characterize systems in terms of asymmetric relations between elements of that system.

Like I said above, this is a highly unpopular and idiosyncratic position to hold, so I’m very interested in hearing your views.

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6 Comments

Filed under Bertrand Russell, Causality, Philosophy, Physics, Science

6 responses to “Thinking About Causality (Part 1)

  1. joshuaupson

    The above post is quite interesting, but it leaves me with a few questions. Also, I apologize in advance if this reply is poorly written; I’m on my way to a dinner engagement and don’t have long to write.

    My primary question is this: How do you distinguish your view from that of the classic Humean view of causality? Basically, what I am asking for is a distinction between these claims:

    Theory of Causation (Trin): Causation is the way in which we characterize systems in terms of asymmetric relations between elements of that system.

    Theory of Causation (Hume-ish): Causation is simply the way we describe constant conjunctions we observe between objects in the world. [We never see a "cause", we just see that event X precedes event Y with regularity and "imagine" there must be some such relationship.] [I know this isn't the best distillation of Hume, I apologize.]

    Aside from the obvious changes in terminology, in what ways do you and Hume seem to differ?

    [I apologize if the above is in any way vague or paints an unfair view of either theory, but as I noted, I am in a bit of a rush to get this question out before dinner and have little time for editing.]

    Cheers.

    • Ok, while it’s been a long time since I’ve really read Hume closely, let me try to differentiate the two approaches. In An Inquiry to Human Understanding, Hume provides two related definitions of cause, one to capture the “external” impression and the other to capture the “internal” impression. First, on p. 76, he says that a cause is “an object, followed by another, and where all objects similar to the first are followed by objects similar to the second,” is alleged to be the experience that provides us with the notion of the constant conjunction, the connection between pairs of events. Now, his second definition provides the internal sensation of causation, the sense of determination (in W. E. Morris’ words–a Hume scholar with a nice SEP entry). Here Hume says that a cause is, “an object followed by another, and whose appearance always conveys the thought to that other,” (p.77).

      It seems to me that both of these approaches to understanding causation are psychological in nature; one deals with the empirical and experiential nature of causation and the other deals inferential patterns of the mind when thinking about the relation between two events. Now, I don’t want to commit myself to any story about the psychological nature of the brain or the relation between psychology and causation WITHOUT some evidence coming out of cognitive science to back me up. For the position I want to defend (and the one I’ve thrusted on Pearl, perhaps illegitimately), I can safely remain agnostic vis-a-vis the psychology question, which I think is a boon at this point.

      So, in the sense described above, my position is even more minimal and eliminativist than is Hume’s position; whereas he rejected the metaphysical interpretation of causation and put in its place a psychological interpretation, I am rejecting the metaphysics and suggesting that causation is only one (of many) means of systematically investigating a physical system.

      Scott, you’re probably better able to reproduce some Hume than I am…any ideas?

      • I have really enjoyed this post. I had really been thinking about what Russell’s comment that Pearl quoted since reading the Epilogue. I actually must admit I had not known Russell had made this point about causation before. As for Hume, I studied him mostly out of interest for his position on the origin of ideas and his views on various kinds of relations. I will have to think about this more.

        I imagine the whiplash response to this position is a charge of monism? If you are not analyzing causal relations in a metaphysical category, then are you suggesting that the universe has no first cause? If causation inherently has a level of priority, then the notion of time is the notion of cause, thus if causation has not a metaphysical but only epistemological element how do you get back to the study of time? Now I am guessing this is not the point. You are not denying some level of metaphysics to causation but you are suggesting that is not the primary issue? For example, I generally see probability-judgments not metaphysically but epistemologically. I see our understanding of probability as based upon our data and our finite variables that we have collected to generate models. Much of the variation is not inherent to reality its inherent to the limits of our knowledge, our interpretation, and what things we know to put into the models for statistical inference. I am going to just assume that you are not suggesting in this conception of causation as epistemic that you are getting into a monistic view, on the contrary I assume what you are suggesting is by concentrating on causal relations as epistemically driven you wish to avoid all these questions altogether within the analysis?

  2. Pingback: Hume’s Causality Problem: An Introduction | The Modern Dilettante

  3. Pingback: Thinking About Causality (Part 2) | The Modern Dilettante

  4. Nice post, Scott. I started addressing the question of how much metaphysics we should be doing when thinking about causation in Part 2, but it’s interesting to bring up again and again. So here’s the question: what is the appropriate level of metaphysics we should be engaging in when thinking about science and causation? I have two answers to this question that I’ve been operating from for a while now. First, if we’re talking about a priori metaphysics, then I think we shouldn’t be doing any (apologies to the history of philosophy). Now, if instead we’re doing empirically-informed metaphysics, then I think it’s permissible to do some SO LONG as those claims are backed up with empirical evidence. But what I can’t stand are “cherry-pickers” who look for empirical evidence to back up their metaphysics; instead, the metaphysical claims made should be subject to the evidence of our best science.

    Regarding the problem of monism you mention, and the problem of time, I think that the safest course of action is to develop a position that is hopefully agnostic vis-a-vis those problems. Personally, the problem of a first cause is, if anything, a problem for cosmologists, but I’m doubtful as to whether any legitimate evidence can be offered in favor of a theory of ultimate origins of the universe that could establish the case in favor of one or the other. So I’m being an unabashed naturalist here and stating that the monism problem is a physics problem (if it is a problem at all) and if/when they provide evidence one way or the other then I would need to address the problem of whether my conception of causation is in accordance with that position, but until then I do not want my metaphysics to guide my initial analysis of causation (which the problem of time or the first cause is until there’s evidence one way or the other, I think, but that’s contestable).

    This is admittedly a hardcore position, and if pushed I’ll claim that my position is pretty anti-metaphysical and that the burden rests with any defender of a metaphysical claim to show that it’s a fault of the minimalist conception that any tension between that minimalist conception and some metaphysics is a problem for me and not for the metaphysics. So how successful do you think this response will be? I’m pretty certain that it won’t stand on its own, and at some near point I’ll try to provide a more comprehensive and sympathetic defense of that view. But the point will be the same; namely, that any analysis of causation should begin with a minimalist conception and only emend that conception when it is empirically necessary to do so. So if given the criticism that the minimalist conception is in tension with the metaphysics of time or the problem of the first cause, I’ll ask for some reason as to why these problems are (1) real empirical problems and (2) why an account of causation should be in accordance with them.

    What do you think?

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