- (Premise) I am the only entity that has all the conscious states I presently have.
- (Premise) I am breathing.
- (Premise) My soul isn't breathing.
- (Premise) My brain isn't breathing.
- I am neither my soul nor my brain. (2-4)
- Neither my soul nor my brain has all the conscious states I presently have. (1,5)
- (Premise) If my soul or my brain is conscious, it has all the conscious states I presently have.
- So, neither my soul nor my brain is conscious.
If my soul or my brain grounds my consciousness, it does not ground my consciousness by being conscious. It grounds my consciousness by having non-conscious states that ground my consciousness. These non-conscious states will then be more fundamental than my conscious states.
In particular, substance dualists should agree with naturalists that conscious states are non-fundamental. Only non-substance dualists, like hylomorphic dualists and property dualists, have a hope of saying that conscious states are fundamental. And of course a similar argument can be run for other mental states beside the conscious ones.
In practice, some substance dualists will say that I am my soul. If so, then I don't breathe (at most I cause breathing), I don't weigh anything, and so on.