Keith at Summa Philosophiae surveys J. P. Moreland’s argument for substance dualism (via Philosophers’ Carnival). The first premise is that there are subjective experiences that require indexical (first-person) language and thus, are not reducible to third-person characterizations. As support for this claim, Moreland points to the unique nature of self-knowledge. If indeed there are fundamentally privileged first-person perspectives, then physicalism, which implies that everything is “exhaustively describable from a third-person point of view in terms of objects, properties, processes, and their spatiotemporal locations”, is false. Keith offers the following formal argument:

(1) Statements using the first-person indexical ‘I’ express facts about persons that cannot be expressed in statements without the first-person indexical.

(2) If I am a physical object, then all the facts about me can be expressed in statements without the first-person indexical.

(3) Therefore, I am not a physical object.

(4) I am either a physical object or an immaterial substance.

(5) Therefore, I am an immaterial substance.