Does Quantum Mechanics Invalidate the Law of Non-contradiction? Part 1

Post Author: Bill Pratt

This seems to be a common misconception, one that I have seen many times on the blog. Recently, one of the most helpful commenters on the TQA blog, Walt Tucker, wrote a detailed response to this claim as a comment on another post. He has given me permission to share his commentary in this blog post. Every word below is Walt’s unless I indicate otherwise, and I thank him for giving me permission to use his excellent response.

A friend of mine was using his apologetics know-how with an atheist and using principles that are self-evident in nature, such as the law of non-contradiction, to argue for the existence of God. The atheist claimed that quantum superposition violates the law of non-contradiction and thus my friend’s whole argument was null and void. Knowing that I have knowledge in quantum theory and apologetics, my friend asked whether quantum superposition does violate the law of non-contradiction.

Since this comes up so often with skeptics and atheists who try to use arguments from quantum mechanics against the classical apologetic argument for the existence, or at least the certainty of the existence, of God, I thought I would post my reply to my friend here for all of my Christian friends to use who might come across a person who tries to use the ill-fated quantum approach against God. (Of course God created the quantum world, so it isn’t so likely that such arguments can be used against His existence. Such attempts show either a misunderstanding of the nature of God, or a misunderstanding of nature itself.)

Before I present the reply, I need to give some background on how the argument the atheist is using arises in quantum mechanics. There is a classic experiment used to demonstrate the non-intuitive nature of the quantum world. It is called the two-slit experiment. Light is made up of discrete packets of energy called “quanta.” You can never have a half, or any fraction of, a quanta. In one sense, it is like having a gum ball from a gum ball machine. You get a whole gum ball. You can smash it, chew it, or whatever, but you still have the same about of gum and it only comes in whole gum balls.

So, light is generated from atoms and absorbed by other atoms as quanta packets of energy (called a photon). The light we see in a room with a typical incandescent light bulb is many millions of quanta, so one quanta of photon energy is very, very small. In the experiment, a single quanta of light is shot towards the double slit (see figure below).

There is a piece of film on the other side. When both slits are open, the light appears to go through one of the two slits and be absorbed by the film at one point at a random position. But when this is done over millions of shots, the image on the film is an interference pattern as if the photons went through both slits at the same time (the image on the film is the classical wave interference pattern of light). An interference pattern is the crossing pattern you see when you drop two pebbles in a pond as the same time and the waves interfere – high crests and low crests – with light it is bright and dark areas.

But since only one photon is shot at a time, it is odd that the film shows an interference pattern when intuition would say a particle of light, the photon, would only go through one slit or the other, but couldn’t go through both. To test that, one can put a detector at the slits to try and see if the photon goes through one slit or the other, or both. When that is done, the photons are detected at only one slit or the other, randomly, and the interference pattern on the film disappears (it is what you would expect if the photons did go through only one slit or the other).

So, knowing which slit the photon goes through destroys the interference that appears on the film that would appear when you don’t know which slit the photon goes through. Quantum mechanics is a mathematical formulation of this behavior for predicting the outcome of experiments called observations. Each detection on the film would be an observation. As such, what is called an observation does not require a human observer, but does require some sort of detector, whether it be a film, a photo-detector, or anything that could absorb the photon. Now knowing the weird behavior of the quantum world, I give the reply to the question.

[Bill Pratt] In part 2 of this series, Walt completes his explanation as to why quantum mechanics does not violate the law of non-contradiction.

Tags: law of non-contradiction, Quantum mechanics, two slit experiment, Walt Tucker

This entry was posted by Bill Pratt on Monday, January 2nd, 2012 at 9:00 am and is filed under Science and God. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

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Bill Pratt

Comments

Todd

Bill/Walt,

I’d be interested in what argument the apologist was using to argue for the existence of god. My guess is that we do not need to invoke the law of non-contradiction to effectively argue against the claim…
http://walttuckerministry.shutterfly.com Walt Tucker

Todd, he was using a form of the cosmological argument derived from first principles. Regardless of whether you can argue against the claim without invoking the law of non-contradiction, the fact is that it is very common to do so. Some atheists and skeptics will toss what they think is a grenade from the quantum world when it turns out to do nothing. Again, regardless of whether logic is timeless and independent of any possible world, which is a whole other discussion, it is a misunderstanding that QM violates this logic principle. Part II will show that.

It is odd that people will claim science has proved the principles of logic are not valid when it is the very principles themselves that form the basis of the scientific method. If you pull the rug out from the foundation of the very method used to discover something, the discovery becomes void.
Andrew Ryan

The only people I hear using QM or the laws of logic to argue on this subject are theists.
http://walttuckerministry.shutterfly.com Walt Tucker

Andrew, I’ve not heard of a theist use QM to argue for the existence of God. But I’ve heard many atheists use the QM case against. You might be lumping logic and QM into the same thing. They aren’t all the same thing. Many theists do argue from logic for the existence of God. The QM trump card is used quite frequently these days as some post-moderns try to make a case that logic is like language and is only a construction of man’s thinking. However, again, they are pulling the rug out from under their own arguments. If the principles of logic are not sound, they have no basis for making any kind of argument that anybody should take seriously.
Andrew Ryan

Nope Walt, I’m not mixing them up. I’ve heard theists using BOTH as evidence. To be honest, there’s not much that apologists won’t try to use as evidence for a God – pretty much everything is fair game. I’ve never heard an atheist making the arguments you say you’ve heard, so I guess we’ve both got one on each other!
Andrew Ryan

Out of interest Walt, do YOU subscribe to the ‘logic as proof of God’ argument? If so, what counter-scenario would you expect to see in the absence of God?

If it is a universe without, say, the Law of Non-Contradiction, exactly what would that look like? How would one describe such a universe without encountering the same problems you point out exist when one attempts to deny the LNC?

Thanks

“some post-moderns try to make a case that logic is like language and is only a construction of man’s thinking”

That’s not really the same as saying that the LNC doesn’t exist.
http://walttuckerministry.shutterfly.com Walt Tucker

Ryan,

To your last statement, if logic is merely a language construct, then it doesn’t exist outside of the mind. So, for the post-modern, it is saying the same thing.

To your question, I accept that logic principles, such as the LNC, exist in any possible universe, even no universe. So, i cannot envision a universe where it would not be true.

I view the timeless existence of logical principles as proof of an ultimate God. How that relates to any particular religion is a whole other matter that should be discussed in another dialogue.
Andrew Ryan

Tucker, thanks for your answer. I do think you are contradicting yourself though – if the LNC exists in any possible universe you can’t use it as a proof of God, as it would exist even in a Godless universe.

No, saying it is a construct of the mind is not the same as saying it doesn’t exist.
http://walttuckerministry.shutterfly.com Walt Tucker

Dear Andrew, it seems you do not understand this. We are not talking the same thing, or at least you aren’t pay attention to the words I use and are putting your own words in place.

For example, your last sentence, “saying it is a construct of the mind is not the same as saying it doesn’t exist.” I’d agree with that statement. However, that is not what I said. I said that if logic is MERELY a construction of the mind, then it doesn’t exist OUTSIDE of the mind. There is a big different between that and what you said.

My claim about God and logic principles was that logic is true in any possible universe. Then I said that timeless logic principles point to an ultimate God, but that more discussion would be needed as to whether that ultimate God was the god of any of this world’s religions. Let me elaborate so that you can see that a godless universe is not a possible universe if the existence of logic principles point to an ultimate God. My claim is that even atheists believe in a God. They may not believe in the God of any religion, but they do believe in a God. That God is the principles upon which this universe exists. This God is not views as a personal god, the God of the Bible, but merely as the source of the laws which govern the universe. NO ONE can deny that there are principles upon which this universe operates. If they did, they couldn’t believe science is possible. So, when you say a godless universe, you can only mean a universe absent of the gods of the religions.

For the record, I’m not advocating that the ultimate God is impersonal and only principles. To make that point is beyond this discussion. But, at a minimum, there is some undeniable God that is the ultimate source of this universe that even an atheist can’t deny. For anyone to claim otherwise means they still don’t understand what I’m claiming.
Andrew Ryan

Walt, I’m paying absolute attention to your words (you’re the one who mixed up my surname and first name!)

Saying LNC doesn’t exist outside the mind is still not the same as saying “A can equal not-A”. One can argue that it’s a language construct as it’s basically just about the definition of ‘is’. A is A. If it wasn’t, the word ‘is’ would have no meaning.

It’s an enormous stretch to say atheist believe in Gods if you define Gods as logical principles. Anyone can ‘prove’ theism by coming up with an arbitrary definition of Gods – I can define ‘Gods’ as a ham sandwich and say that my fridge therefore proves the existence of Gods!
Andrew Ryan

In your most recent post you’re still not addressing the problem if your two competing claims:
1. Logical absolutes could not be any other way.
2. The fact that the absolutes are the way they are is evidence for God/s

These two cannot both be true. If you’re saying ‘phenomena x is evidence for effect y’ you’re saying that there are two scenarios, we observe X or we do not observe it, and the former is evidence for Y. If you maintain the latter scenario is even hypothetically impossible, then we’d observe X with or without effect Y.
Andrew Ryan

Walt: “But, at a minimum, there is some undeniable God that is the ultimate source of this universe that even an atheist can’t deny. For anyone to claim otherwise means they still don’t understand what I’m claiming”

No, you don’t get to stick the label ‘God’ on anything YOU can’t explain. This is classic ‘God of the gaps’. And it doesn’t help to say that anyone who points this out just doesn’t understand your argument.

“…a godless universe is not a possible universe if the existence of logic principles point to an ultimate God.”

The key word there is ‘IF’. It’s a circular syllogism: you’re basically saying “X must be so IF the existence of Y points to X”, with ‘Y pointing to X’ being the thing you actually need to demonstrate. See this: “A universe without dragons is not possible if those footprints I just saw point to dragons”. OK, well show us that dragons are a likely cause.

Your point can be re-phrased thus: “I believe that the existence of logic principles point to an ultimate God.”

And since you’ve already agreed that logic principles MUST exist, you’ve already shown that the fact of their existence cannot be used to point to anything.

So what would a Godless and hence logic-less universe look like? How would one know one was in it? What would the evidence be?
http://walttuckerministry.shutterfly.com Walt Tucker

Andrew, sorry about mixing your name up. Notice I had it correct last time. I’m not sure why I did that other than absently mindedly seeing the Ryan part of you name and typing it without thinking.

We still have a misunderstanding between us. I never claimed number 2. Also, your statements about the LNC shows you are still trying to argue about its existence when all I had been saying is what post-moderns say.
http://walttuckerministry.shutterfly.com Walt Tucker

Andrew, I don’t care what label you want to put on it. Call it Santa Claus if you want. The fact is that there are principles of the universe that no one can deny in their right mind. That was all I was saying. I believe it does lead to the existence of God in the way we generally understand the label, but “I” have not made that argument here. You have been arguing with me about something I hadn’t even presented an argument for. I was merely responding to your posts about what I believe.

If you want to have a serious argument about the existence of God, then we need to lay it out correctly (and do it rationally, rather than off the hip) and do that in another thread. Arguing for God’s existence was not my goal here. Here, I was showing why QM does not violate LNC. Then you took me down a rabbit trail that is not even consistent with what I did say.

If you want to talk about labels and not ham sandwiches, what is your definition of what a “god” is? We would have to agree on that first. I’ve been using the definition of “ruler” of the universe. That was not arbitrary. As such, a ham sandwich would not qualify!
Andrew Ryan

Walt, I was merely pointing out that it’s nonsense to say atheists believe in God, as long as one is able to define God as ‘ruler of the universe’. We don’t need to call them ‘God’, we already have perfectly good terms! This is bait and switch, debating subterfuge. Observing that the universe follows rules is not the same as saying it has a ruler, any more than observing that snow falls must necessitate a ‘snow maker’.
http://walttuckerministry.shutterfly.com Walt Tucker

Andrew, that is not a bait and switch. The definition of a “god” from its historical meaning is “ruler.” Kings were gods. Judges in the ancient context where gods. By extension, a “God” is the supreme ruler. It was by that definition that it was also thought in ancient times that gods were behind phenomena in the world. I am not resorting to this last sense for what a “god” is because I am not claiming at this point whether the essence of the principles that govern the universe is personal. Whether that ruler is personal is part of the argument I didn’t give. I am being consistent and using the definition correctly as it is historically understood. I think the only reason you don’t like the “label” is because it has connotations your don’t like. Or, because I would end up claiming, if I gave you the rest of the argument, that this supreme God, and the God of Judeo-Christian religion is the same. It is with that argument that I expect you to disagree with me, not the one I’ve been making.

By the way, snow does have a snow maker. You think snow just appears out of nowhere? The snow maker might be a process just like an ice cream maker is a machine, but some process does exist which produces snow. Therefore, there is a snow maker. Is there a creator of the universe? Did it come into existence? Then there is a creator. Again, the only question which I think separates the theist from the atheist is whether that creator is personal, or a pure physical process with no origination, no ability to make decisions, and no has no intention behind its actions. It doesn’t matter what you call this creator, what matters is whether it is personal or not, or even whether there is something beyond it that might be personal. That really is the question.
Andrew Ryan

Excellent, you understand my analogy about snow. So because snow is made by natural processes, you’re happy not to apply a ‘ruler’ label to the processes creating it. Before these processes were known, would you have used that label, or just said ‘we don’t yet know’?.

And all this is before we get into the question of whether the LNC can even be said to ‘rule’ anything in any sense beyond metaphorical.

Chess has rules, I can be said to believe in their existence, but no-one says there is any kind of ‘chess ‘god’.

These word games do not help you.
Andrew Ryan

If you’re now saying you do not claim the second option, that you do not point to logic as evidence of God, then I’m a bit lost as to what you actually believe, so perhaps we should just let that drop.

I’m guessing we appear to agree that the laws of logic could not be any other way, in any universe, and therefore presumably in Godless ones.

You want to give the label God to simple descriptions of the way reality works. I think such a label is uneccesary and misleading. You think I don’t like it for ideological reasons. Equally I think you DO like it so you can somehow claim atheism doesn’t actually exist. So perhaps we’ll leave that too. Which leaves…

I don’t think that saying ‘LNC is a construct of our minds’ is part of post modernism. And I don’t think it’s equivalent to denying it exists. LNC is basically the label we’ve invented to sum up saying ‘that rock isn’t itself and not itself at the same time’. It’s practically tautology. Saying this is a mental construct is not the same as saying ‘the rock can be itself and not itself’. Rather, it’s saying that without minds to observe it you’ve just got a rock. You can say ‘right, but even with no minds, that rock is still itself’, but then you’re still using the mental construct of LNC to describe it, even when imagining it’s existence in the absence of minds.
http://walttuckerministry.shutterfly.com Walt Tucker

Andrew, changing what a person says to suit your own position doesn’t help you either. You’ve done it on practically every post.

I meant the ‘ruler’ label to be applied to the snow making process. I never changed what I was saying nor played word games. I have been very consistent, but evidently unable to communicate. You are hung up on the God of the gaps and I haven’t been talking about that anywhere. Where have I used the label “god” for something I don’t have an explanation for? The best I can figure is that you have an argument in your head that you are debating against here rather than actually interacting with what I say. Arguing against a strawman argument that is not my argument isn’t very fruitful. I’ve been trying to interact with your statements even though they are outside the topic.

Indeed chess has rules. Do those rules govern how you play chess? They do, but then a game like chess is different than processes that operate the universe. Chess is more like moral rules than physical rules. But, since you brought chess up, did someone create the rules of chess? Considering that they are rational rules, a creator of those rules would have to be a rational person, wouldn’t they? What does it mean to be rational? I’d say it means that a person follows the timeless logical principles. Why does a person have to follow such principles to be considered rational?
Andrew Ryan

So if being subject to rules means you have a God by your logic, given that your God is also subject to the LNC, does that mean your God also ‘has a God’?

Regarding people arguing that LNC is a mental construct, I can make up a rule off the top of my head that is a mental construct and yet is still undeniable. It is impossible for me to click my fingers and turn into an elephant. Is that a ‘rule’? Is it like a ‘God’ by your definition? Is arguing that it’s a mental construct equivalent to arguing that it isn’t actually true? This seems to be your argument with LNC – that calling it a mental construct is the same as arguing against it.
http://walttuckerministry.shutterfly.com Walt Tucker

Andrew, to your first paragraph, that is my point. You’ve been assuming what I believe without looking at what I actually say. I think you probably think you are addressing what i say, but it seems to have been transformed by the argument you want to make.

To your second paragraph. I agree with the first part. I only agree with the second half if I assume by godless you mean the god of religions. I’ve tried to make the point that a godless universe in the truest sense of the word is impossible. Also, I’m not saying atheism doesn’t exist. Obviously there are a lot of atheists around. But an atheist, as I understand the word, is one who doesn’t believe there is a personal God, especially as revealed in religions. When I say this, I am using the true definition of the word “god.” It isn’t just a label, but a meaning. There is no word games, but plain simple use of words. You can say a “label” is unnecessary and misleading, but the word is more than a mere label (labels are arbitrary for the most part). Whether you want to use a different label doesn’t matter to me. What matters is that the meaning is the same. When I use the word “god,” and more specifically “God,” I am using a very specific meaning if I keep to the oldest sense of the word rather than the religious sense.

And to your last paragraph. I agree with you. But, regardless of what you believe post-moderns say, in fact there are things they say. In the last century, in the study of language, they had come to say exactly what I said they say. You should study the topic sometime, but be sure to pay attention to what they say (even if it is ultimately meaningless), not what your views are of what they should say. (BTW, I used to do that when I was younger – arguing with what people should say, rather than what they do say. However, I have learned that the rule of philosophy is to engage the argument, not just give your own views. That is not to say you don’t give your own views, but they need to relate to the views of the other person as well. That being said, the academic post-modern world would disagree with your views of logic, even though I agree with your view because I think it is the sensible view.)
http://walttuckerministry.shutterfly.com Walt Tucker

Andrew, to your last sentence first – for the hundredth time, I didn’t make that argument. Post-moderns make that argument.

To the first paragraph, that is a great question. But to answer that in the way I think you are looking at it, you have to answer the question first of whether that God is a personal God. If it is the non-personal sense, the ultimate ruler, then it is the ultimate and has always existed. There is nothing over it. It is self existing and self governing. In the personal sense (which I haven’t tried to show yet), God is subject to Himself – He cannot do anything that violates His own nature. If you noticed, the answer is the same whether God is impersonal or personal. However, when you said “subject to,” I gathered that either you still didn’t understand that logic principles would be an aspect of the ultimate or you were thinking of the personal God who it seems would be subject to something as we are. Either way, the ultimate is self-governing to its own nature.
http://sandwichesforsale.blogspot.com/ DagoodS

Having lurked through this blog entry, its follow-up, and the comments, a few questions arise.

Article: Since this comes up so often with skeptics and atheists who try to use arguments from quantum mechanics against the classical apologetic argument for the existence,…

1. Since it comes up “so often” I would think a link or two would be easily obtained, although a quick goggle whack did not discover any atheistic arguments regarding this topic. (I did find one, but that devolved into TAG, and the uselessness that is the conversation within that argument.) Can someone point out a good link or two (since it comes up “so often”) that provides the formal argument for why quantum mechanics contradicts the law of non-contradiction and the implication that has on theism? Thanks.

2. I guess we could define “God” so broadly that everyone believes it exists…but why should we? Isn’t the benefit of language the ability to narrow our conversation toward understanding by limiting definitions? I could equally define “tennis racket” to mean every item that strikes a ball in a sport…but you would be very surprised how difficult it would be to play tennis with a baseball bat defined as a “tennis racket.”

The difficulty we non-theists have is getting theists to define “God” with enough distinction we can figure out what we are talking about. When the only way they can sustain “God” is to so broadly define it, it could mean anything…well…that doesn’t bode well for persuasive argument.

3. Not sure who all these terrible “post-moderns” are out there in the world—how will I know whether I am one of these odious beasts?
http://walttuckerministry.shutterfly.com Walt Tucker

Dagood,

First, I assure you, based on previous conversations, you are not one of the obnoxious beasts. Such are the ones that deny absolute truth exists. In other words, all truth is individual truth and subjective. As a trial lawyer, I don’t think you could hold to such beliefs and be in business for very long. The term “post-modern” isn’t all that new. Try Richard Rorty or Jacques Derrida for more information.

Second, I am surprised people think I am arbitrarily defining “God” to fit what ever I want. I will grant that if I say “God” most people have something in mind that is very religious in nature. But I also know that when I talk to people of various religions, their concept of “God” can vary drastically from one another. The only common denominator, and the one that relates to the historical meaning of the word, is a “ruler,” regardless of whether it is personal or impersonal. So, without considering any particular version of “god,” I am using the most basic historical definition. A baseball bat cannot serve properly as a tennis racket, and thus the analogy does not do well. Better is to use the analogy of a police car, where there are many kinds, but there is a common denominator.

You ask for a precise definition of “God,” but it makes sense to use the common definition as the starting point and then start pointing out the distinctions between the kinds of gods.

Third, my and others who have run into the QM argument against the LNC comes up in conversations. I have not read it anywhere, although I have had it come up in dialogues like this one, especially with other physicists. Most of the people that have mentioned it to me are knowledgable about QM, whether professionally, or as amateur enthusiasts; or are post-moderns who will use it, but don’t know much about it. I will look and see if I can find someone using the QM argument on the internet to which I can give a link. I assure you that if you ask just about any Christian apologist, they will have run into this. Some skeptics may have not run across it because they aren’t making a claim that someone would use that against.
http://walttuckerministry.shutterfly.com Walt Tucker

In my search, I see part of the problem. There are two parts to this. The one that has to do with QM and logic. The other with the use of logic as first principles in the argument for the existence of God (the Kalam argument). It looks there is plenty of stuff on the internet for the two parts. It is more difficult to find them together. I did find the following, for what it is worth:
http://www.rationalskepticism.org/creationism/debunking-the-kalam-argument-for-god-t24039-60.html
Andrew Ryan

Walt, I’m sorry that the exchange has been frustrating for you – is the problem that I was hearing ‘Lnc etc is evidence for God’ and your point was actually ‘Lnc IS God’?

If so, apologies again. I think part of the problem is that I’m baffled by such a loose definition.

Also, LNC seems to basically be “It makes no sense to say that that boulder is a rock and also not a rock”. This isn’t a ‘rule’ or law in the same sense as, say, the law of gravity. I can still understand people who make the argument that it’s basically a construction of language. It’s just self explanatory. I am genuinely open to being persuaded otherwise though. NB, I may have fallen into making the case for that myself, but started off just trying to explain why I didn’t see the ‘language construct’ argument as being equivalent to denying the LNC, regardless of whether I accepted the argument or not myself.
http://walttuckerministry.shutterfly.com Walt Tucker

Andrew, I think it is best to have a precise definition at the onset of an argument rather than a vague one. In general, when ten different people try to define what they understand the meaning of the word “god” to be, you will get ten different and inconsistent answers. However, if you try to arrive at the root of the various meanings and include the historical meaning in the determination of the root, you can get a more precise definition, not a loose one.

I agree LNC is different than gravity. We have no basis to say gravity is the same in all possible universes. However, we do have a basis to say that about the principles of logic, principles of mathematics, etc. Gravity does rule aspects of nature, but it is not likely an ultimate rule and thus is derived from a higher rule.

I was using the term “god” in a very specific sense in relation to logical principles. You were continuing to use it in the religious sense where I had not made that claim (yet). I am uncomfortable with saying LNC IS God, but prefer to say principles of logic are an aspect of God in the sense that they are part of the ultimate rule of the universe. But I was claiming that an atheist would have to believe that at least their are rules that govern the universe. Anymore than that requires more development of the argument. I never went beyond that.

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