On Philosophy

September 23, 2006

Causal Closure Over Observables

Filed under: General Philosophy — Peter @ 12:10 am

One of the assumptions of materialism is that the physical world is completely causally closed. Even though this proposition is well supported by evidence some would doubt it (perhaps reasoning that causal closure is broken only in rare cases, and thus explaining why it hasn’t been revealed by our scientific investigations). What is impossible to doubt, however, is that the universe of observable phenomena is casually closed. And if we define as physical that which is observable, which not a radical suggestion, this in turn implies that the physical world is completely casually closed.

If it is indeed the case that the observable world is causally closed it must be the case the all the causes of something observable are themselves observable. This should seem intuitively plausible, since if we observe effects it seems reasonable to suppose that we can deduce information about the causes, making the causes observable. This is, of course, not to say that the causes are necessarily observable with our current level of technology, simply that they are observable in principle. For example, we can observe atoms through a scanning tunneling microscope by observing their effects on a stream of electrons; atoms did not suddenly become observable when the scanning tunneling microscope was invented, rather it was the case that they were observable but we simply lacked the tools to directly investigate them.

Let’s say for example that some observable phenomena, X, can be caused by two factors, A an B, either independently or in combination. If we observe X then we can only deduce that A or B (or both) are the cause, and this is not enough to consider A and B observable. However, if A and B are observably different they must differ in some observable property. And if they differ in some observable property that must mean that they can cause different observable effects, and thus we could set up additional tests to determine which of the factors is a cause of X, making them observable. Given this there are only two possibilities if the observable world is not to be completely causally closed. One is that X is caused by two different factors, A and B, which differ only unobservably. This claim, however, is essentially saying that only the observable properties that A and B have in common are responsible for X, and thus the observable phenomena are still causally closed. (A possible rejoinder to this case is to suppose that there is some third factor, C, that shares the same observable properties as A and B, but differs in an unobservable property, and isn’t a cause of X. However, this is a contradiction, because by observing X we would know that A and B didn’t have the unobservable property that differentiate them from C, and thus the property isn’t unobservable after all.) The other possibility is that there are two factors that can cause X, A and B, and that while A is observable B is unobservable. However, to avoid the pitfalls outlined above, we further stipulate that whenever B is the cause of X A is as well (perhaps because of some other factor). If this was a possible situation then X would indeed have an unobservable cause, but this situation too hides a contradiction. The contradiction is made evident when we consider what reasons we have to say that one thing is the cause of another. In either the senses of a sufficient or necessary cause we say something is a cause of some state, Q, when the absence of that thing would have prevented Q from occurring, or if that thing by itself could have brought about Q. B can play neither of these roles, since we stipulated that it is necessarily accompanied by A, and thus it can’t be the case that it brings about X by itself, nor can it be the case that its absence prevents X from being brought about, since A is a cause, and thus B isn’t really a cause at all. Again, the observable phenomena are completely causally closed.

From this reasoning we conclude that, by our notions of observable and cause, the observable world must be completely causally closed. And if we define as material that which is observable then the material world is also completely causally closed. Some may object, saying that there are no material causes for observable conscious states, and hence that we can’t claim the observable is identical with material. This would be a problem if we allowed all conscious experience to count as observable, however, as presented here, we can take as observable to mean only those phenomena observed with our outward-directed senses, and the causal closure holds just as well. And from that we could deduce by observing other people that our conscious states really do have a basis in the material / observable, or that they are unobservable by our outward-directed senses but have no causal powers (they are epiphenomenal). And if we reject epiphenomenalism (see here) then we can conclude that the mind really is identical with some material phenomena.

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5 Comments

  1. One of the assumptions of materialism is that the physical world is completely causally closed. Even though this proposition is well supported by evidence some would doubt it (perhaps reasoning that causal closure is broken only in rare cases, and thus explaining why it hasn’t been revealed by our scientific investigations).

    Evidence? Hume would say that you can’t show that any two events must be causally connected. (Of course, he nevertheless advocated assuming that all events have a material cause.)

    Of course, I’m just being picky with that, but it does lead to a larger problem in a way. To say X has a cause requires that you can identify X as an X at arbitrary times. However, this is not always the case. For quantum mechanics (even in the non-Copenhagen, non-crazy interpretations), it’s said that you can’t identify X as X without accidentally changing it to X′. The same problems apply for A and B, creating A′ and B′, so quantum physics are left with the problem that they can only say what they think must have been the case at time₀ after they observe facts about that time later (at time₁). Which means that the relationship of A or B causing X becomes a sort of noumenon, out of the reach of our phenomenal observation.

    Which all gets back to the post the other day where I advocated verb based metaphysics, and you said, “That’s identity over time, not identity.” But there is no identity that’s not identity over time, or at least, no philosophically productive way to use identity which isn’t. At the very least, we need to be able to bring up the same thought of some X at two different times and know that we’re having the same thought of X in order to make a constructive judgment with it, so we need to know thought(X)₀ === thought(X)₁ even in the case that both Xes are considered to be at the same time.

    Of course, I’m a determinist, so it’s a bit odd that I’m defending ignorance of causation so much. The real thing I’m getting at is, the assumption of universal causation is just that, an assumption. It’s a good one, and maybe even a necessary methodological one for human technological advancement, but it’s still an assumption nevertheless.

    Comment by Carl — September 23, 2006 @ 2:08 am

  2. “Hume would say that you can’t show that any two events must be causally connected.”

    No, Hume said you can’t PROVE it, you can show it to be very very very likely. This is why I said “well supported by evidence” not “conclusively proven”.

    “But there is no identity that’s not identity over time, or at least, no philosophically productive way to use identity which isn’t.”

    Um, see logic.

    “For quantum mechanics (even in the non-Copenhagen, non-crazy interpretations), it’s said that you can’t identify X as X without accidentally changing it to X'”

    Um, no, you just end up chaning the position or momentum. If I am observing an election it remains an electron.

    “Which means that the relationship of A or B causing X becomes a sort of noumenon, out of the reach of our phenomenal observation.”

    Again, no, see the scientific method.

    Sure Carl if you had only one specific data point deducing causation would be impossible, but that is not the case. You objections all fall away when you realize that you can observe the same kind of result many different times.

    Comment by Peter — September 23, 2006 @ 10:01 am

  3. “Hume would say that you can’t show that any two events must be causally connected.”

    No, Hume said you can’t PROVE it, you can show it to be very very very likely. This is why I said “well supported by evidence” not “conclusively proven”.

    Like I said, I was being nitpicky with that.

    Um, no, you just end up chaning the position or momentum. If I am observing an election it remains an electron.

    Ah, but before when the discussion was about the identity of a person, you said the person’s position was a part of their identity. Now you deny it? Remember, a person’s identity can’t be a matter of having the same electrons, since its constituent parts are always changing.

    Sure Carl if you had only one specific data point deducing causation would be impossible, but that is not the case. You objections all fall away when you realize that you can observe the same kind of result many different times.

    But the whole question I’m raising here is “how do we know that what I observe at time 1 is the same sort of thing as I observe at time 2?” It all comes down to a question of “what is the same?” which it turns out has a lot of presuppositions built into it.

    See also: Kant

    Comment by Carl — September 23, 2006 @ 2:16 pm

  4. “Ah, but before when the discussion was about the identity of a person, you said the person’s position was a part of their identity. Now you deny it? Remember, a person’s identity can’t be a matter of having the same electrons, since its constituent parts are always changing.”

    Today’s post is about causal closure, not about identity (see title). As you should know causual relations by their nature deal with types of things, and are only instantiated in individual occurances. And to be clear I didn’t say that a person was defined by all the physical properties of the individual, you did in this statement: “Let’s say there’s me and there’s something with all the same physical properties as me.”

    “But the whole question I’m raising here is “how do we know that what I observe at time 1 is the same sort of thing as I observe at time 2?” It all comes down to a question of “what is the same?” which it turns out has a lot of presuppositions built into it.”

    Because they share certain properties, although not all the same properties. They are part of the same natural kind, and causal relations are between kinds.

    And after Aristotle Kant is one of the philosophers whose work I find least relevant, occasionally he came up with a good idea (ex: categorical imperative), but he rarely supported them properly, and his metaphysics was just wacky.

    Comment by Peter — September 23, 2006 @ 3:43 pm

  5. Great article… I’m in the middle of writing on the topic and thoroughly enjoyed reading.

    Comment by Matthew D. — July 10, 2007 @ 9:19 am


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