1. Hamiltonian mechanics is almost an unfalsifiable tautology
In the OP, I wrote:
avoiding (1) is kinda silly—if I try to avoid talking about (1), then I find myself tripping over (1) in the course of talking about lots of other things that are of direct practical interest.
I think Hamiltonian mechanics passes that test. If my friend says that Hamiltonian mechanics is stupid and they don’t want to learn it or think about it ever, and then my friend spends some time trying to answer practical questions about practical physics systems, they will “trip over” pretty much every aspect of Hamiltonian mechanics in the course of answering those questions. (Examples include “doing almost anything in quantum mechanics” and “figuring out what quantities are conserved in a physical system”.)
The real crux is I think where I wrote: “I have yet to see any concrete algorithmic claim about the brain that was not more easily and intuitively [from my perspective] discussed without mentioning FEP.” Have you? If so, what?
Hamiltonian mechanics is applicable to both atoms and [stars]. So it’s probably a bad starting point for understanding atoms
If somebody says “As a consequence of Hamiltonian mechanics, stars burn hydrogen”, we would correctly recognize that claim as nonsense. Hamiltonian mechanics applies to everything, whereas stars burning hydrogen is a specific contingent hypothesis that might or might not be true.
That’s how I feel when I read sentences like “In order to minimize free energy, the agent learns an internal model of potential states of the environment.” Maybe the agent does, or maybe it doesn’t! The free energy principle applies to all living things by definition, whereas “learning an internal model of potential states of the environment” is a specific hypothesis about an organism, a hypothesis that might be wrong. For example (as I mentioned in a different comment), imagine a very simple organism that evolved in an extremely, or even perfectly, homogeneous environment. This organism won’t evolve any machinery for learning (or storing or querying) an internal model of potential states of the environment, right? Sure, that’s not super realistic, but it’s certainly possible in principle. And if it happened, the FEP would apply to that organism just like every other organism, right? So the sentence above is just wrong. Or we can interpret the sentence more charitably as: “The free energy principle makes it obvious that it may be evolutionarily-adaptive for an organism to learn an internal model of potential states of the environment.” But then my response is: That was already obvious, without the FEP!
Ditto for any sentence that says that anything substantive (i.e. something that might or might not be true) about how the brain works as a consequence of FEP.
3,4,5,7
I think Hamiltonian mechanics makes some important aspects of a system more confusing to think about, and other important aspects of a system much easier to think about. It’s possible that one could say that about FEP too; however, my experience is that it’s 100% the former and 0% the latter.
As above, I’m interested in hearing concrete plausible claims about how the brain works that are obvious when we think in FEP terms and non-obvious if we don’t.
In the OP, I wrote:
I think Hamiltonian mechanics passes that test. If my friend says that Hamiltonian mechanics is stupid and they don’t want to learn it or think about it ever, and then my friend spends some time trying to answer practical questions about practical physics systems, they will “trip over” pretty much every aspect of Hamiltonian mechanics in the course of answering those questions. (Examples include “doing almost anything in quantum mechanics” and “figuring out what quantities are conserved in a physical system”.)
The real crux is I think where I wrote: “I have yet to see any concrete algorithmic claim about the brain that was not more easily and intuitively [from my perspective] discussed without mentioning FEP.” Have you? If so, what?
If somebody says “As a consequence of Hamiltonian mechanics, stars burn hydrogen”, we would correctly recognize that claim as nonsense. Hamiltonian mechanics applies to everything, whereas stars burning hydrogen is a specific contingent hypothesis that might or might not be true.
That’s how I feel when I read sentences like “In order to minimize free energy, the agent learns an internal model of potential states of the environment.” Maybe the agent does, or maybe it doesn’t! The free energy principle applies to all living things by definition, whereas “learning an internal model of potential states of the environment” is a specific hypothesis about an organism, a hypothesis that might be wrong. For example (as I mentioned in a different comment), imagine a very simple organism that evolved in an extremely, or even perfectly, homogeneous environment. This organism won’t evolve any machinery for learning (or storing or querying) an internal model of potential states of the environment, right? Sure, that’s not super realistic, but it’s certainly possible in principle. And if it happened, the FEP would apply to that organism just like every other organism, right? So the sentence above is just wrong. Or we can interpret the sentence more charitably as: “The free energy principle makes it obvious that it may be evolutionarily-adaptive for an organism to learn an internal model of potential states of the environment.” But then my response is: That was already obvious, without the FEP!
Ditto for any sentence that says that anything substantive (i.e. something that might or might not be true) about how the brain works as a consequence of FEP.
I think Hamiltonian mechanics makes some important aspects of a system more confusing to think about, and other important aspects of a system much easier to think about. It’s possible that one could say that about FEP too; however, my experience is that it’s 100% the former and 0% the latter.
As above, I’m interested in hearing concrete plausible claims about how the brain works that are obvious when we think in FEP terms and non-obvious if we don’t.