Is a feeling of pain just a pattern of neurons firing?

Type physicalism says yes. On this view, a feeling of pain doesn't come with a brain process. It is one. Think of lightning. Lightning isn't a glowing thing caused by an electrical discharge. It simply is the discharge. Dualism treats mind and body as two different things. This theory, also called mind-brain identity theory, says there was only ever one thing, described two ways.

The British philosopher Ullin Place launched the idea in 1956. He argued that mental processes shouldn't be defined by behaviour. They should be identified with states of the nervous system. When he died, he left his own brain to the University of Adelaide. The psychologist E. G. Boring had laid out the logic back in 1933. If two events always happen together, at the same time and place, they aren't two events. They're one.

The theory's biggest problem is called multiple realizability. Pain goes with different nervous-system states in different animals. Yet every one of them is in pain. Think of corkscrews: very different gadgets can all do the same job. If pain can be built in many ways, how can it be one specific brain state? The identity theorist J. J. C. Smart replied that this alone doesn't prove the theory false.

A second worry goes deeper. Even a full list of firing neurons may not capture what pain feels like. That gap between brain facts and felt experience is what the Mary's room thought experiment was built to dramatize.