Materialism, according to APA Dictionary of Psychology, is the philosophical position that everything, including mental events, is composed of physical matter and is thus subject to the laws of physics. From this prospective, the mind is considered to exist solely as a set of cerebral processes. This philosophy can be traced back to ancient times but gained a new impetus from advances in the physical sciences beginning in the seventeenth century. Originally, the causes of behavior were to be found in the material of the body, particularly the nervous system. More recently, the focus has been the cerebral system: the brain.