The spiritual is immaterial and not bound by space and time. Everything material is extended, spatial, and temporal. How can something mental, like a decision of will, have a physical effect? Can a sensation like pain be reduced to neurophysiological processes, or is a sensation more than just those processes? These are questions of the philosophy of mind, one of the most important research areas in contemporary philosophy. The introductory course Philosophy IV presents the key theories of contemporary philosophy that attempt to answer these questions. Unlike all other introductory writings on the mind-body problem, this text also provides an answer based on Aristotelian-Thomistic philosophy, which proves to be a genuine alternative to both dualism and materialism.