This chapter digs deeper into the problems about why uncovering laws of human action is so difficult and then shows social science how to proceed the way natural science does. These problems go back to the so-called mind-body problem, first identified by René Descartes in the seventeenth century. He argued that the mind can’t be the brain, and that mental processes generally—thought, feeling, sensation—can’t be physical, material brain processes. Social scientists may ignore this issue, but philosophers cannot. Understanding arguments claiming that our mental lives cannot be physical processes is indispensable. Otherwise, one cannot grasp the dispute between naturalism and interpretationalism as they attempt to explain human action.