Contemporary arguments for forms of psycho-physical dualism standardly depart from phenomenal aspects of consciousness ('what it is like' to have some particular conscious experience). Conceptual aspects of conscious experience, as opposed to phenomenal or visual/perceptual
ones, are often taken to be within the scope of functionalist, reductionist, or physicalist theories. I argue that the particular conceptual structure of human consciousness makes this asymmetry unmotivated. The argument for a form of dualism defended here proceeds from the empirical premise
that conceptual structure in a linguistic creature like us is a combinatorial and compositional system that implicates a distinction between simple and complex, or 'atomic' and 'molecular' concepts. The argument is that conceptual atoms, qua atoms, are irreducible to anything
else. If so, and if the atoms are essentially semantic, a form of dualism follows: though positively inviting naturalistic inquiry into the semantic and mental aspects of nature, it requires that we look at the mental as a primitive domain of nature. Schematically, then, the argument is as
follows: (1) Human consciousness/thought is conceptually structured. (2) The human conceptual system is a 'particulate' system at a syntactic and semantic level of representation (the notion of a 'particulate' system is developed in Section 2). (3) This implies the existence
of conceptual 'particles', concepts that have no further semantic decomposition ('atoms'). (4) A conceptual atom cannot be explained in terms of anything that does not involve its own intrinsic properties (Section 3). (5) Physicalism as normally conceived is inconsistent
with (3) and (4) (Section 4).