3 ms·

Well, I'm glad then that we get to skip the bit were I have to spell out the facets of the argument I made. (Over on reddit bringing this up usually means me h

Well, I'm glad then that we get to skip the bit were I have to spell out the facets of the argument I made. (Over on reddit bringing this up usually means me having to gently prod the other person to read up on hidden variable theories so they can tell me if that is what they meant by phrases like "something determines it we just can't see what".) I'm actually a compatibilist about "free will", so I've no need for a ghost in the machine or to be flipping quantum coins in my head. The point of my comment was simply to point out that "our universe is deterministic", full stop, isn't a warranted premise by current evidence. If you only meant "adequately deterministic" by "deterministic", fine and dandy. However, I don't know anything that actually stops the two causal chains A and B in my thought experiment from being macroscopically very different. So skipping the "adequately", I feel, gives those not familiar with the details a misleading impression that we can unproblematically think of ourselves as just in the old clockwork universe. (Thus the kinds of phrasing I see a lot on reddit from the loosely-informed on such matters.) (Edits: silly grammar and spelling stuff.)

jessriedel 15y ago
OK, I support being precise with our terminology. What I was trying to emphasize is that, with regards to discussion of "free will", the important thing about "adequate determinism" isn't predictability. It's that we can trace back all causes to known (possibly intrinsically probabilistic) physical "stuff", with no room for a soul.
- jaylevitt 15y ago
  Something I've been wondering, and I'm way out of my depth here - would determinism be something that could eventually find an explanation in information theory? My layman's argument against determinism was something like: OK, even if my biological self is making my decisions for me, how does it get the inputs that drive those decisions? Imagine a simple exercise study, conducted without face-to-face contact. Half of the participants are told to exercise, and half are told not to. At the end, the half that is told to exercise will have exercised more often than the half that did not. Therefore, if the world is deterministic, what's "sending" that determinism from the study to the participant? My conclusion was: I dunno, information is flowing? Though I guess that's where quantum mechanics comes in, and I guess there's probably also an information-theoretic aspect to that.
  - jessriedel 15y ago
    Not sure I know what you're asking. If we ignore quantum mechanics, then all of our empirical evidence strongly suggests that the universe is strictly deterministic. (Although this conflicts with our intuition about our own consciousness.) What that means is that if we were to have the position and velocity of every particle at a given moment in time we could (in principle) calculate the position and velocity for any future moment. The important thing is that the known and understood physical "stuff" is just particles, and the only thing that can or need be known about them is their position and velocity. There is no thing-which-is-NOT-made-of-particles which we might call a soul or whatever. In particular, you could in-principle predict what experimental subject Bob would chose based on the configuration of the particles in the universe before he was born. So, is your question "How is that pre-Bob configuration of particles causing Bob's choice?" If so, then you just look to the fundamental laws of classical physics: particles obey certain rules which govern how they move around. Given a certain pre-Bob configuration, we would compute that the particles would all follow certain trajectories which eventually would lead to a configuration where many particles were assembled into Bob himself, and these particles moved in such a way (according to known physics) that Bob (who is composed of the particles) made a certain choice. Or is your question about quantum mechanics?
    - jaylevitt 15y ago
      I guess my question is about "how does that propagate?" I have no physics background, so maybe the answer is obvious, but I have trouble intuiting how, in my thought experiment, the experimenter and the subject have any shared state.
      - jessriedel 15y ago
        Oh, ok. That's just a manner of understanding how humans work (when viewed as a machine). The experimenter has some idea in his head which is encoded in the connections between neurons (although no one knows how...which is why it's hard to be totally confident that people are deterministic). This idea is translated into vocal cord vibrations and lip movements, which vibrate air in a certain way to product sound. This sound wave travels to the subject's ears. It is translated into electrical signals traveling on neurons by the ear, leading into the subject's brain. This changes the state of the subject's brain (the connections between the neurons) in such a way that a day later, while going through his normal routine, the subject's brain directs him to exercise.
jerf 15y ago
It should be pointed out that Bell's inequalities only rule out the existence of classical hidden variables being able to explain quantum effects, which if one understands the history behind the question makes sense. Technically it doesn't (and can't) rule out hidden variables that are "quantum" in nature (if you'll permit me the shorthand), but from our perspective those are the very definition of a needlessly multiplied entity in the Occam's Razor sense. Nevertheless, that simply means they aren't useful to us, not that they don't exist. It is certainly possible to imagine that we exist in a simulation in which the simulation is "quantum", but whenever a random number is needed, a psuedorandom and deterministic source is used instead. We'd never be able to tell from the inside, unless there was something very, very broken about the psuedorandom number generator, which given that we are talking about something with the capacity of simulating our entire universe seems unlikely (unless intentional). Basically, our universe could be deterministic from the outside while being nondeterministic on the inside, in the sense that those of us on the inside will never be able to collect enough information to predict our own universe's evolution from the inside. (In other news, I'm in the camp that considers "randomness" and "lack of knowledge" to be two phrasings of the same thing, so it's sensible to talk about things being deterministic(/"not random") from one viewpoint but nondeterministic from another.) This is just FYI since it's relevant, not disagreement.
- jessriedel 15y ago
  > It should be pointed out that Bell's inequalities only rule out the existence of classical hidden variables being able to explain quantum effects No, Bell's inequality rules out all local hidden variables, whether those variables are generated deterministically or not. Bell's inequality does not say anything about the existence of intrinsic randomness in the universe; it says something about locality. (Of course, the fact that quantum mechanics is intrinsically random as far as we can tell made it conceptually very difficult to formulate the correct inequality, although the math was simple. That's why the original EPR paper couldn't quite nail down what was so weird about QM, even though they were on the right track. It was an astounding feat by John Bell.)

jessriedel 15y ago

OK, I support being precise with our terminology. What I was trying to emphasize is that, with regards to discussion of "free will", the important thing about "adequate determinism" isn't predictability. It's that we can trace back all causes to known (possibly intrinsically probabilistic) physical "stuff", with no room for a soul.

jaylevitt 15y ago
Something I've been wondering, and I'm way out of my depth here - would determinism be something that could eventually find an explanation in information theory? My layman's argument against determinism was something like: OK, even if my biological self is making my decisions for me, how does it get the inputs that drive those decisions? Imagine a simple exercise study, conducted without face-to-face contact. Half of the participants are told to exercise, and half are told not to. At the end, the half that is told to exercise will have exercised more often than the half that did not. Therefore, if the world is deterministic, what's "sending" that determinism from the study to the participant? My conclusion was: I dunno, information is flowing? Though I guess that's where quantum mechanics comes in, and I guess there's probably also an information-theoretic aspect to that.
- jessriedel 15y ago
  Not sure I know what you're asking. If we ignore quantum mechanics, then all of our empirical evidence strongly suggests that the universe is strictly deterministic. (Although this conflicts with our intuition about our own consciousness.) What that means is that if we were to have the position and velocity of every particle at a given moment in time we could (in principle) calculate the position and velocity for any future moment. The important thing is that the known and understood physical "stuff" is just particles, and the only thing that can or need be known about them is their position and velocity. There is no thing-which-is-NOT-made-of-particles which we might call a soul or whatever. In particular, you could in-principle predict what experimental subject Bob would chose based on the configuration of the particles in the universe before he was born. So, is your question "How is that pre-Bob configuration of particles causing Bob's choice?" If so, then you just look to the fundamental laws of classical physics: particles obey certain rules which govern how they move around. Given a certain pre-Bob configuration, we would compute that the particles would all follow certain trajectories which eventually would lead to a configuration where many particles were assembled into Bob himself, and these particles moved in such a way (according to known physics) that Bob (who is composed of the particles) made a certain choice. Or is your question about quantum mechanics?
  - jaylevitt 15y ago
    I guess my question is about "how does that propagate?" I have no physics background, so maybe the answer is obvious, but I have trouble intuiting how, in my thought experiment, the experimenter and the subject have any shared state.
    - jessriedel 15y ago
      Oh, ok. That's just a manner of understanding how humans work (when viewed as a machine). The experimenter has some idea in his head which is encoded in the connections between neurons (although no one knows how...which is why it's hard to be totally confident that people are deterministic). This idea is translated into vocal cord vibrations and lip movements, which vibrate air in a certain way to product sound. This sound wave travels to the subject's ears. It is translated into electrical signals traveling on neurons by the ear, leading into the subject's brain. This changes the state of the subject's brain (the connections between the neurons) in such a way that a day later, while going through his normal routine, the subject's brain directs him to exercise.

jerf 15y ago

It should be pointed out that Bell's inequalities only rule out the existence of classical hidden variables being able to explain quantum effects, which if one understands the history behind the question makes sense. Technically it doesn't (and can't) rule out hidden variables that are "quantum" in nature (if you'll permit me the shorthand), but from our perspective those are the very definition of a needlessly multiplied entity in the Occam's Razor sense. Nevertheless, that simply means they aren't useful to us, not that they don't exist. It is certainly possible to imagine that we exist in a simulation in which the simulation is "quantum", but whenever a random number is needed, a psuedorandom and deterministic source is used instead. We'd never be able to tell from the inside, unless there was something very, very broken about the psuedorandom number generator, which given that we are talking about something with the capacity of simulating our entire universe seems unlikely (unless intentional). Basically, our universe could be deterministic from the outside while being nondeterministic on the inside, in the sense that those of us on the inside will never be able to collect enough information to predict our own universe's evolution from the inside. (In other news, I'm in the camp that considers "randomness" and "lack of knowledge" to be two phrasings of the same thing, so it's sensible to talk about things being deterministic(/"not random") from one viewpoint but nondeterministic from another.) This is just FYI since it's relevant, not disagreement.

jessriedel 15y ago
> It should be pointed out that Bell's inequalities only rule out the existence of classical hidden variables being able to explain quantum effects No, Bell's inequality rules out all local hidden variables, whether those variables are generated deterministically or not. Bell's inequality does not say anything about the existence of intrinsic randomness in the universe; it says something about locality. (Of course, the fact that quantum mechanics is intrinsically random as far as we can tell made it conceptually very difficult to formulate the correct inequality, although the math was simple. That's why the original EPR paper couldn't quite nail down what was so weird about QM, even though they were on the right track. It was an astounding feat by John Bell.)