If feel only fits your narrow, human centric definition of it, then of course machines can't feel pain. There isn't much point in having a discussion if the discussion is about your understanding of a word though.
If you go by the broader definition of feel, which includes "to have a sensation of something", then I'd argue that the line is far more blurred.
If you accept that a rat is capable of feeling pain, then surely you must accept that a functionally identical machine with a neural network functionally the same as a rat's brain can also feel pain? There's no real fundamental physical reason stopping us constructing a computer which functions in the same way as a rat's brain does. Does the computer we constructed suddenly stop being a machine?
My understanding of "feel" is purely subjective. I think it's impossible to create an objective definition. That's the problem
"To have a senseation of something" isn't really helpful definition, because "have a sensation" is just another word for "feel". It's like saying that the definition of "to buy" is "to purchase".
Physics cannot, even in theory, explain my subjective experience of pain. Why do I feel pain, when my brain's atoms are in specific positions?
If you go by the broader definition of feel, which includes "to have a sensation of something", then I'd argue that the line is far more blurred.
If you accept that a rat is capable of feeling pain, then surely you must accept that a functionally identical machine with a neural network functionally the same as a rat's brain can also feel pain? There's no real fundamental physical reason stopping us constructing a computer which functions in the same way as a rat's brain does. Does the computer we constructed suddenly stop being a machine?