What is a “mental” process? The stuff we’re conscious of or a limbo between real, wet, neural processes and observable behavior?
A well known analogy is the computer. The hardware stuff you can kick is analogous to the brain; the stuff you see on the screen is, I suppose, the phenomenology; then the software, all of which correlates with processes you could detect in the hardware if you looked hard enough, some but not all of which affects the screen, is cognition.
Forget for a moment about minds and consider the engineering perspective; then the point of the levels is clear. When you want, say, to check your email, you probably don’t want to fiddle around directly with the chips in your PC. It’s much less painful to rely on years of abstraction and just click or tap on the appropriate icon. You intervene at the level of software, and care very little about what the hardware is doing being the scenes.
What is the point of the levels for understanding a system? Psychologists want to explain, tell an empirically grounded story about, people-level phenomena, like remembering things, reasoning about things, understanding language, feeling and expressing emotions. Layers of abstraction are necessary to isolate the important points of this story. The effect of phonological similarity on remembering or pragmatic language effects when reasoning would be lost if expressed in terms of (say) gene expression.
I don’t understand when the neural becomes the cognitive or the mental. There are many levels of neural, not all of which you can poke. At the top level I’m thinking here about the sorts of things you can do with EEG where the story is tremendously abstract (for instance event-related potentials or the frequency of oscillations) though dependent on stuff going on in the brain. “Real neuroscientists” sometimes get a bit sniffy about that level: it’s not brain science unless you are able to talk about actual bits of brain like synapses and vesicles. But what are actual bits of brain?
Maybe a clue comes from how you intervene on the system. You can intervene with TMS, you can intervene with drugs, or you can intervene with verbal instructions. How do you intervene cognitively or mentally? Is this the correct way to think about it?