3 ms·

True, but there was Ben-Hur's thesis that "a chariot is capable of carrying any person", which says as much about brains as the Church-Turing thesis does unless

True, but there was Ben-Hur's thesis that "a chariot is capable of carrying any person", which says as much about brains as the Church-Turing thesis does unless you beg the question.

mitthrowaway2 3y ago
Do you mean that it's begging the question to assume that the brain comes to its conclusions via a physically deterministic procedure that terminates in finite time?
- eru 3y ago
  > [...] to assume that the brain comes to its conclusions via a physically deterministic procedure [...] I don't think determinism makes any difference here? There are various flavours of non-deterministic Turing machines, and whether the brain is deterministic is more of a philosophical question than anything else. (I would say it's convenient and proper to model the brain as using a lot of random noise, eg even if just from thermal noise. And that kind of biological cellular level is the probably the 'right way' to think about the brain in most circumstances. One could try to argue that the noise comes from deterministic chaos. And then someone else could argue that the underlying quantum processes are already non-deterministic. And yet another person can argue that quantum mechanics is completely deterministic, if you go by the many worlds interpretation and not the silly Copenhagen Interpretation of quantum mechanics. Etc)
- omnicognate 3y ago
  That's not what the Church-Turing thesis is about. The Church-Turing thesis says that any "effective procedure" (i.e. algorithm) for performing computations on natural numbers is equivalent to a Turing machine. It is generally accepted but cannot be proven because "effective procedure" is not defined. Indeed it can be seen as providing a definition for the term "effective procedure". To extend that to say anything about the physical world (i.e. some form of "Physical Church-Turing Thesis") is to make quite a different assertion and one that is not so "generally accepted". To make it say anything about brains you have to assert some form of equivalence between brains and "effective procedures" on the natural numbers, which is indeed to beg the question in this instance. There's a different idea you may be confusing it with, which is the idea that since the known laws of physics (aside from state vector reduction in quantum mechanics) are in the form of differential equations that can be numerically integrated to arbitrary precision anything can be "simulated". However, this is not part of the Church-Turing thesis. (And personally I find the phrase "to arbitrary precision" here, and the exception for state vector reduction, quite a barrier to basing any assertions about the nature of the universe or minds on it.)
  - sgt101 3y ago
    There are different levels of argument depending on the precision of the definition of the concepts in play, which is unhelpful in general but also unavoidable. I think that the folk definition of computation is so wide and vague that almost any physical process can be characterized as a computation in that sense. So brains (being physical) must be (folk) computers. The problem is that this doesn't get us anywhere because there are lots of equivalences and for practical purposes in there and what we really need is a characterization of the brain as it operates rather than what that operation might be modeled as. As Searle says, you can simulate the processes of digestion but that doesn't mean that you have an artificial stomach that can turn food to energy.

True, but there was Ben-Hur's thesis that "a chariot is capable of carrying any person", which says as much about brains as the Church-Turing thesis does unless you beg the question.

mitthrowaway2 3y ago

Do you mean that it's begging the question to assume that the brain comes to its conclusions via a physically deterministic procedure that terminates in finite time?

eru 3y ago
> [...] to assume that the brain comes to its conclusions via a physically deterministic procedure [...] I don't think determinism makes any difference here? There are various flavours of non-deterministic Turing machines, and whether the brain is deterministic is more of a philosophical question than anything else. (I would say it's convenient and proper to model the brain as using a lot of random noise, eg even if just from thermal noise. And that kind of biological cellular level is the probably the 'right way' to think about the brain in most circumstances. One could try to argue that the noise comes from deterministic chaos. And then someone else could argue that the underlying quantum processes are already non-deterministic. And yet another person can argue that quantum mechanics is completely deterministic, if you go by the many worlds interpretation and not the silly Copenhagen Interpretation of quantum mechanics. Etc)
omnicognate 3y ago
That's not what the Church-Turing thesis is about. The Church-Turing thesis says that any "effective procedure" (i.e. algorithm) for performing computations on natural numbers is equivalent to a Turing machine. It is generally accepted but cannot be proven because "effective procedure" is not defined. Indeed it can be seen as providing a definition for the term "effective procedure". To extend that to say anything about the physical world (i.e. some form of "Physical Church-Turing Thesis") is to make quite a different assertion and one that is not so "generally accepted". To make it say anything about brains you have to assert some form of equivalence between brains and "effective procedures" on the natural numbers, which is indeed to beg the question in this instance. There's a different idea you may be confusing it with, which is the idea that since the known laws of physics (aside from state vector reduction in quantum mechanics) are in the form of differential equations that can be numerically integrated to arbitrary precision anything can be "simulated". However, this is not part of the Church-Turing thesis. (And personally I find the phrase "to arbitrary precision" here, and the exception for state vector reduction, quite a barrier to basing any assertions about the nature of the universe or minds on it.)
- sgt101 3y ago
  There are different levels of argument depending on the precision of the definition of the concepts in play, which is unhelpful in general but also unavoidable. I think that the folk definition of computation is so wide and vague that almost any physical process can be characterized as a computation in that sense. So brains (being physical) must be (folk) computers. The problem is that this doesn't get us anywhere because there are lots of equivalences and for practical purposes in there and what we really need is a characterization of the brain as it operates rather than what that operation might be modeled as. As Searle says, you can simulate the processes of digestion but that doesn't mean that you have an artificial stomach that can turn food to energy.