A reader's e-mail with my comments in blue:
Nice post on the LNC. That topic is a real quagmire, isn't it?
I’ve lost the link to the Science Daily report of the Cleland experiment, so the details of how he confirmed the superposition are lost to me, but I’m really struck by the fact that you are defending LNC as a transcendental, not transcendent, principle. Kant doesn’t take this route in the First Critique, does he? LNC is not some form of sensibility, is it?
That's right, I am defending LNC as a transcendental, not a transcendent principle, and for two reasons. First, I believe that LNC is well-nigh unassailable if presented as a transcendental a priori condition of the possibility of (i) meaningful discourse and (ii) experience of the objects of Sellar's manifest image or of Kant's phenomenal world, with (i) being more unassailable than (ii). Second, the transcendental defense is all I need to turn aside what I take to be your conclusion from the Cleland experiment, namely, that there are macro-objects of direct perceptual acquaintance that serve as counterexamples to LNC. To show that LNC applies beyond our thought and beyond our experience to whatever lies beyond our thought and experience, if anything, is not so easy. One cannot just dogmatically assume that a law of thought is automatically a law of reality, especially since this has been denied by any number of philosophers. Aristotle in Metaphysics Gamma, 3, 4, attempts a proof by retortion of LNC, but as far as I can see, all he establishes is that LNC is a necessary condition of meaningful thinking and speaking, not that its validity extends beyond thought and speech and their objects to things in themselves.
I would also urge in passing against certain dogmatic Thomists that the Critical Problem — the problem of showing how a priori conditions of thinking apply to things external to us — is already present in nuce in Aristotle. But that's another long series of posts.
LNC is surely not a form of sensibility for Kant, but it is a form of understanding. Since there is for Kant no experience (Erfahrung) without a 'marriage' of sensibility (Sinnlichkeit) and understanding (Verstand), it seems reasonable to impute to Kant the view that no macro-object of experience can violate LNC.
One thing I think Cleland would say is that observing the paddle in the normal sense, i.e, bombarding it with lots of photons, disturbs the superposition and collapses the ambivalent quantum state into a moving or a not moving state. So he would seem to agree with you as far “seeing” in the ordinary sense goes. We don’t see something moving & not moving—and one could add: our eyes and brains are just not designed to experience such objects even if we could do so without disturbing them. But, seeing is not the same as sensing, and presumably the paddle in its quantum state has effects (on us) that are unambiguously different from its effects in states where the superposition has collapsed. So, as you say, no naked eye observations of superposition, but perhaps that’s too narrow a focus and we should admit that we might experience a superposition is some other unique way.
You seem to be assuming the Copenhagen interpretation of QM. But as you know, it is not the only game in town. Bill Hill, a U.K. immunologist, e-mailed me the following, which is very helpful:
There are two main interpretations of quantum mechanics which are popular in the physics community (there are a few others, but they are mostly propounded by eccentrics). The first is the "Copenhagen" interpretation, in which quantum events really do exist in multiple incompatible states at the same time, but only when there is no outside observer looking at them. I am not making this up, though I should add that by "observer", they do not just mean conscious beings but any information-carrying system (such as a sensor) which can report data about the quantum event. Though it is implausible at first glance, this interpretation does in fact solve the boundary problem that so vexes many scientists. Because sub-atomic particles are too small for us to see, they are free to exhibit this behaviour. But people, planets and so on are so large that they are always under observation in some sense, they cannot behave in this way. Hence, when the little bit of metal in the article is observed, it will either appear moving or not moving to the person looking at it, but when nobody is looking it is in fact doing both. This raises enormous questions about perception and causality, and many people are very unhappy with it as a result. The important point is that your suggestion that there cannot be an empirical counterexample to the Law of Non-Contradiction remains intact under the Copenhagen interpretation.
The most popular alternative to Copenhagen is the "Many-Worlds" interpretation, in which the universe splits into two duplicates every time a quantum event occurs. So when the little bit of metal in the article is put into its quantum state, in one universe it is moving, and in the other it is not. Of course, it is impossible for us to tell which one we are in. Many people (rightly, in my opinion) think that this is just silly, and embrace Copenhagen on grounds of parsimony. However, it is consistent with the data, and also with the Law of Non-Contradiction, since two incompatible states cannot exist in the same universe under Many-Worlds.
So as far as I can tell from my limited experience, you are correct and neither the Copenhagen nor the Many-Worlds interpretations of quantum mechanics offer an empirical counterexample to the Law of Non-Contradiction, whatever other fascinating philosophical questions they may raise in their own right.
The salient point is that, on the 'many worlds' interpretation of QM there is no violation of LNC not even on the micro-level let alone on the macro-level. Given that there is no one settled interpretation of QM accepted by all physicists, the case against LNC at either level is bound to be weak.
This is very tricky stuff, but I think it is the paddle, a macro object that we can directly observe under other conditions, that is now in the superposition state of moving and not moving. We in fact have put it into this state. The paddle is not some ding an sich, but an ordinary object that can transition from existing “normally” in one state or its opposite to existing at once in both contradictory states. In principle any macro-object could be reduced to such a quantum ground state but we just can’t physically do so.
I am afraid that you are not making sense. You have already granted that the paddle that we see with the naked eye cannot be seen by the naked eye to be both moving and not moving, But now you are saying that that very visible paddle — and not some invisible micro-constituents of it – has been put by the experimental apparatus into a state in which it is both moving and not moving. This implies that one and the same visible paddle is both (moving & not moving) and not (moving & not moving). Which is is higher -order contradiction.
Are you saying that there are two paddles? Then they can't both be visible.
Furthermore, if you say, as you do above, following the Copenhagen interpretation, that observation of the paddle forces it into one state or the other, then cannot also say that that very same visible paddle is in both states.
I am afraid that the science journalist's report on the Cleland experiment has delivered us into a realm of rank gibberish.
Your second point that LNC is also a “form of intelligibilty” is surely right, and it just invites incomprehension to say that the paddle is both moving and not moving. I guess we need to learn the jargon of the physicists here. I’m not sure exactly what they say but something like the paddle in its quantum ground state is in a superposition of motion and no motion. That I get, and it says something remarkable about the really weird universe we apparently live in. I’m saving up my money and moving to a good old Newtonian universe at the first opportunity!
But now you are sounding like certain Trinitarian theologians who say that we should just repeat the creedal formulae without worrying whether or how they make any bloody sense. It is curious that defenders of the coherence of the Trinity often bring up QM. You of course grant no authority to the Bible or the Church. Why then do you genuflect before the authority of scientists when they spout gibberish? I am being intentionally provocative. ComBox is open if you care to counterrespond.
