The word religion encompasses a broad range of beliefs, practices and institutions. It has been defined in diverse ways by scholars in many fields, including anthropology, history, sociology, philosophy, psychology, literature and religious studies. The various definitions reflect a variety of perspectives that have emerged from the multidisciplinary study of religion. Some definitions are functional, describing the beliefs and practices that generate social cohesion or provide orientation in life. Others are substantive, referring to the qualities that distinguish a religious phenomenon from other members of a category.
For example, the Greek philosopher Thales (6th century bce) and the Athenian Heraclitus (flourished c. 5th century bce) each offered a different scheme of the cosmic order. The former conceived a prime matter from which all things were made; the latter saw a controlling principle that transcended the clash of contrasting forces in the universe.
Sigmund Freud and other psychologists have viewed religion as pathological, a force that encourages irrational thoughts and ritualistic behaviors. But despite such doubts, religion continues to thrive in the world and exert a powerful influence on human behavior.
Anthropologists have studied tribal and other “primitive” societies and sought to explain their religions. For instance, the French Abbe Bergier (1718-90) characterized primitive religion as belief in spirits that arose from a variety of psychological causes. The German socialist Karl Marx (1818-83), on the other hand, argued that religion was just an expression of working-class economic suffering and acted as the opium of the people.