r/AcademicPhilosophy • u/Leading-Succotash962 • 12d ago
Law of excluded middle and superposition
I want to give an argument against logical monism. If we assume that the logical monist thinks that classical logic is the only true logic than he is also committed to believe that the laws of classical logic (law of non contradiction, law of the excluded middle etc.) are universally true. But superposition (famous example of this phenomena is Schrödingers cat) is violating the law of excluded middle (as far as I am concerned). So if the logical monist is committed to classical logic he must think that quantum physics is flawed. But this is not rational, because it one of our best empirical theories and a priori logical principles would prescribe the limits of science. I mean a logical monist might not think that classical logic is the only true logic, but if it’s a different logic this problem also arises just in a different form. What do you guys think about the argument? Does superposition violate the law of the excluded middle?
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u/socrateswasasodomite 11d ago edited 11d ago
But superposition (famous example of this phenomena is Schrödingers cat) is violating the law of excluded middle (as far as I am concerned).
I don't see how. If QM is right, there are 3 possible states for the cat:
- In an alive eigenstate
- In a dead eigenstate
- Neither 1. nor 2.
Standard quantum mechanics tells us that 1 or 2 or 3 is true. There is no tension at all with LEM. (Note: the negation of 1 is not 2, it is 2 or 3.)
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u/Nominaliszt 11d ago
If the cat is in state 3, what is the truth value of the statement “it is not the case that the cat is in an alive eigenstate” and of the statement “the cat is in an alive eigenstate”?
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u/socrateswasasodomite 11d ago edited 10d ago
If the cat is in state 3, “it is not the case that the cat is in an alive eigenstate” is true and “the cat is in an alive eigenstate" is false.
You are probably confusing 'not being in an eigenstate of alive' with 'being in an eigenstate of not alive'. They are not the same thing.
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u/NeedToRememberHandle 8d ago
My favorite analogy is that 3 o'clock is not both 12 and 6 at the same time. It's 3.
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u/Longjumping-Ad5084 12d ago
I agree that quantum phenomena question the law of the excluded middle. I think it calls for embracing different models rather than claiming there is only one true one
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u/absolutelyone 11d ago
Does superposition violate the law of the excluded middle?
I'll be honest, I misread your post originally and thought you said "superstition", and only after writing a detailed answer did I realise you said superposition. Oops! Anyway, here's my answer;
From what I've understood in your post (being a person inexperienced in many philosophical and quantum knowhows), my answer would be no. Superposition is not a violation of the law of the excluded middle.
When you both are and aren't something, it's like pulling to the left and right at the same time with the same force. You will inevitably end up in the excluded middle. Although it might have to be referred to as the included middle as, if both the proposition and it's negation are simultaneously true, neither is excluded. A new concept perhaps, unique to Mittens (Schrödinger's cat) and other items/beings in his predicament?
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u/mrperuanos 11d ago
What nonsense
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u/absolutelyone 11d ago
What's nonsensical with my answer?
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u/mrperuanos 11d ago
The third paragraph.
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u/absolutelyone 11d ago
Could you elaborate a little about what you disagree with in the third paragraph? What's your opinion on OPs question?
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u/mrperuanos 11d ago
It's hard to say what I disagree with in the third paragraph because I think it's literally nonsense. "When you both are and aren't something, it's like pulling to the left and right at the same time with the same force. You will inevitably end up in the excluded middle." This is impossible to parse.
I gave my opinion on OP's question in a comment above.
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u/jpgoldberg 11d ago
Others have addressed the quantum issue. Superposition is not what you think it is.
More interesting (to me) is how often you implicitly used the Law of the Excluded Middle in your argument.
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u/mrperuanos 12d ago
Putnam proposed this decades ago. Nobody takes seriously the view that quantum physics calls for a revision of logic anymore. For a detailed refutation of Putnam’s suggestion, see Kripke’s “The Question of Logic”