The central issue here is the nature of persons. Materialism: the only things that exist are material (physical) entities and their properties. Dualistic interaction ism: humans consist of material and immaterial (mental, spiritual) components, and these components interact with one another. That"s all. ideas? is interpreted broadly to include sensations, perceptions, thoughts, etc. Parallelism ? there is a mental realm and a physical realm but they don"t interact with each other. Ordinarily, we distinguish between mental and physical events or states of affairs. A mental event (like an auditory sensation) is an awareness, a state of consciousness. Physical things, events, processes, etc. , are located in space. Physical objects, events and processes are publicly observable; but mental ones are not. Mental entities and states of affairs are private. I make inferences form your appearance, behavior, etc. When you look at the same grass you say that you see green. I always agree with everyone else when we discuss colors.