If there is such a simple argument for physicalism, how come everybody hasn't always been a physicalist? That's a good question, and there is a good answer. The 'causal completeness of physics' wasn't widely accepted until recently.

After all, in supporting phenomenal concepts I am in a sense siding with introspection against the more behaviourist Wittgensteinians. But even so I don't think that introspection is powerful enough to resolve the specific issue about how many colours you can see.

Again, when we view a scene fleetingly, do we consciously see all the details even though we don't retain them, or do we not see them in the first place? Neurological information is crucial to deciding these questions. After all, they are so interesting precisely because unaided introspection cannot resolve them. Rather we need to know what is going on in the brain activities that constitute visual awareness.

The 'phenomenal concept' issue is rather different, I think. Here the question is whether there are concepts of experiences that are made available to subjects solely in virtue of their having had those experiences themselves. Is there a way of thinking about seeing something red, say, that you get from having had those experiences, and so isn't available to a blind person?

The use of neuroscientific data to help resolve phenomenological questions is proving a common theme in much contemporary thinking about the mind. How rich are the contents of visual perception? Does vision only tell us about shapes and colours, or does it also represent higher categories like lemon or umbrella?

Philosophers sometimes also use 'reductionist' more strictly, to mean 'type-identities' between mental and physical categories, and to exclude 'non-reductive physicalisms' like metaphysical functionalism.

I do have quite a lot of sympathy for Fodor's picture of concepts as information-free atomic entities which get locked onto their referents causally, and to that extent they needn't involve anything much in the way of learning. But even so it seems perverse to call them 'innate'. Here we see again the oddity of treating 'not learned' as sufficient for innate.