The religion of the ancient Greeks is startlingly different from Christianity. It has been misinterpreted by people who think that since it is a religion it must be like Christianity, and also by people who think that because it is not like Christianity it is not really a religion at all. The Greeks had poetry that was thought to contain information about the gods, but they had no sacred books that communicated a divine revelation or pronounced dogmas in the authoritative tones of those who claim divine authority for their statements. They had oracles and prophets, official expounders of cult regulations, and priests who were in charge of temples and administered cults, but they had no priesthood in the sense of a clerisy or a church sanctioned by divine authority. In consequence, they had none of the theological disputes, schisms, and religious wars which have been so noticeable a feature of the history of Christianity.

Gods as well as men were ruled by the old Indo-European sky-god, whom the Greeks called Zeus. But there were many gods, and certain principal ones stood out. During the classical period, it became customary to speak of “the 12 gods,” meaning the 12 principal gods. But there were many minor as well as major ones, and new gods could be added to their number. Certain figures of mythology, who were regarded as heroes and thought to be descended from gods, were accorded a form of worship different from that of the gods.

Part of our knowledge of early Greek religion derives from poetry and art; but another part of it derives from prose texts, and in particular from documents relating to cult observances that have been preserved on stone. These different kinds of sources present different aspects of religion, and to a superficial view they seem to present different pictures.

In the earliest Greek poetry that we possess, the great epics of Homer and the Theogony of Hesiod, which names and describes the gods, the gods live together on Mount Olympus under the presidency of Zeus. These gods have not existed since the beginning of time; the first ruler of the gods, Uranus (Heaven) was displaced by his son Kronos, and Kronos was displaced by his son Zeus, who with his brothers, sisters, sons, and daughters was in historic times held to be supreme. They are distinguished from one another by their attributes and functions; thus they form a coherent system in which each deity has his or her special place and relation to the others. Hera is the consort of Zeus and the patroness of marriage; myth portrays her as a jealous wife, resentful of the many unions with goddesses and mortal women which the need for gods and heroes to trace descent from Zeus compels her husband to contract. She is the mother of the craftsman god, Hephaestus, and the war-god Ares; but these two, the one because of his deformity and the other because of his violence and stupidity, are not as highly regarded as some other gods. Hera is not the mother of her husband’s two most important children, Athena and Apollo.

The virgin Athena is the goddess of wisdom, the patroness of women’s work and other crafts, but also a war-goddess more effective than Ares; she was produced by Zeus without a mother. She is the special patroness of Athens, which probably derived its name from her, but she is important in other cities too, including Sparta. Apollo with his sister Artemis, the virgin huntress, is the son of Zeus by Leto, who has no function except that of being their mother; both are archers, but Apollo, lord of the great shrines of Delphi and Delos, is a god of prophecy, a patron of poetry, music, and healing. Only on rare occasions is he said to be a sun god; the sun and the moon belong to minor divinities, Helios and Selene. Hermes, the messenger of the gods, is the son of Zeus by a minor goddess, the nymph Maia. Aphrodite, the goddess of love, is the daughter of Zeus by an obscure deity, Dione. Zeus’ brother Poseidon is lord of the sea, as well as the cause of earthquakes and the lord of horses. Another brother. Hades or Pluto, is the lord of the underworld. Zeus’ sister Demeter, an underworld goddess and responsible for the growth of crops, is the mother of Persephone, the consort of Hades; the mother and daughter preside over the great shrine of Eleusis. The most complicated of the immortals, Dionysus, is usually called the son of Zeus by a mortal princess, Semele, and to begin with had difficulty in establishing his claim to be a major god; he is the god of wine and of ecstasy and the patron of drama. Note that these gods stand for forces that can be seen working in the world.

The myths that provided the early poets with their subject matter show how the gods dealt with each other and with mortals. Men were created not by a ruler of the gods, but by Prometheus, a minor god belonging to the generation displaced by Zeus and his family. The gods rule the universe for themselves, and men have only a minor share of their attention and consideration. Like mortal heroes, the gods care intensely about honor; they demand that men shall honor them. After death the spirits of men lead a shadowy existence in the underworld, in the house of Hades. But the gods have certain favorites among mortals, who in myth are always descended from the liaisons of the gods with mortal men or women, and also favorites among mortal communities.

One god may clash with another; thus in the legend of the Trojan War, Troy is protected by Apollo, Artemis, Ares, and Aphrodite, but is the hated enemy of Hera, Athena, and Poseidon. Zeus is partial to the Trojans, but in the end his partiality is bound to be overcome by the insistence of Hera and Athena. In the Odyssey the return of the hero Odysseus is held up by the enmity of Poseidon, but is finally achieved through the support of Athena, who as Zeus’ favorite daughter has enormous power. The great hero Heracles must contend with the enmity of Hera, always hostile to Zeus’ bastards, but he is protected by Athena. By paying too much honor to one god, one can antagonize another; in Euripides’ play Hippolytus, the hero’s devotion to the virgin huntress Artemis brings upon him the hatred of Aphrodite, the goddess of love. From the aesthetic point of view, this religion has particular advantages; these gods and the myths about them have provided ideal subjects for literature and art, contrasting favorably, it may be thought, with some other religions in this respect.

In the world as it is depicted in early Greek poetry, the will of Zeus always prevails. Although in general the gods care more about their honor than about justice, Zeus is the protector of Dike, the minor goddess who represented justice, and punishes men’s crimes against each other. But since the Greeks, like the ancient Hebrews, could observe that the wicked often flourished like green bay trees, Zeus’ wrath often fell not upon the offender, but upon the latter’s descendants. Zeus was thought to punish crimes against strangers and also suppliants, persons who by an act of submission placed themselves under his protection. But the will of Zeus, like that of other gods, was inscrutable to mortals, who did not live long enough to perceive the working of his justice. Through oracles or through prophets, men might get particles of knowledge from the gods, but this knowledge was thought to be misinterpreted by them. Despite Zeus’ general care for justice, this religion makes it easier to understand why the world is as it is than does a monotheistic religion whose god cares deeply about men, his own creation, and who is altogether good.

So far we have been concerned with Greek religion as it appears in myth. But when we consider the evidence regarding cult and worship in historic times, we find what seems at first a different picture. This kind of evidence takes us nearer to the religion’s origins. The origin of religion is always an obscure subject, and its investigation must be to a certain extent speculative. But it would appear that this religion began with the fear of ghosts; that would explain the importance of the cult of the dead, known from the discovery of tombs to have existed from an early time. After the fear of ghosts will have come the fear of powerful spirits, needing to be placated by offerings, and above all by sacrifice. In the time before the introduction of pasturage and agriculture, a time which has so far been much the longest period of human history, the life of a community depended on the group of male hunters, who disappeared for long stays in the jungle, the abode not only of their game, but of dangerous animals and formidable spirits. Such a spirit will have been the goddess known to the students of the earliest known period of Greek religion as “The Mistress of Animals.” To get their food the hunters had to kill creatures that belonged to her; they had to placate her by giving her back part of its body. Here we have the origin of the sacrifices that were a central feature of Greek religion. But in historic times it was domestic animals, creatures precious to the human community, that were sacrificed to the gods. Not all offerings took the form of blood sacrifices; many were libations of various liquids, a few were holocausts; but blood sacrifice was the most important, and it continued to be offered to the gods of the community right through the history of Greek religion.

In the beginning, the cults centered upon the sanctuaries of the gods seem to have been under private control, in the hands of certain families. In historic times, they belonged to the community, whose welfare was thought to depend on them. Monotheism may well be older than polytheism; it seems that to begin with each community tended to have its special deity. Thus Hera was the great divinity of Argos and of Samos, just as Apollo with his sister Artemis was the great divinity of the sanctuaries of Delphi and of Delos; Athena was the great divinity of Athens, though she had a strong rival in Poseidon. But gradually certain gods acquired an importance that went beyond the localities in which their cults had first developed; thus the early poets depict the gods as living together on Mount Olympus, where each had his or her separate dwelling.

The gods of heaven are distinguished from the gods of earth; in Homer there is very little about Demeter and other earth deities, and offerings to them took a different form from those made to the gods of heaven. Zeus is the father of Demeter’s daughter Persephone, but there is mention of a Zeus of the underworld, who is equated with Hades. Originally Demeter the mother and Persephone the daughter were only different forms of the same being; originally the great god of the underworld was the consort of the earth goddess. Demeter’s temple at Eleusis near Athens was the center of the earliest and most important mystery cult; those who were initiated into her mysteries were believed to obtain certain privileges in the world of the dead. During the sixth century B.C., we first hear of Orpheus, the mythical poet who was supposed to be the author of poems that told a strange story of the birth of Dionysus. He was the child of Persephone by her father Zeus, but was captured and eaten by evil spirits belonging to an earlier generation of the gods, the Titans. But his heart was rescued by Athena and given to Zeus, who then had intercourse with Semele and after her incineration himself gave Dionysus a second birth. The Titans were consumed by fire, and men sprang from their ashes; they were thus a mixture of the evil nature of the Titans and the divine nature of Dionysus. Through Dionysus initiates in the mysteries could attain not eternal life, but a privileged existence in the grave. But it is essential to remember that this kind of belief was current only within a restricted circle, and its theology never became generally accepted. Nor is there any evidence for the once-prevalent belief that the worship of the deities of earth came earlier than that of the deities of heaven, or that a matriarchal phase preceded a patriarchal phase.

The worship of the gods was closely bound up with the social structure of all early Greek communities. Often they were worshiped in splendid temples, some of which, like those at Athens, Delphi, and Olympia, have left notable remains. Festivals in their honor were observed at regular intervals, and played an important part in the life of the communities; people came from far off to visit great religious centers, like the sanctuaries of Zeus and Olympia in the Peloponnesus and Dodona in Epirus, of Apollo at Delphi and in the island of Delos, of Athena at Athens. The four great contests in which athletes from all Greek cities competed were celebrated every four years at Olympia and Delphi, and every two years at the shrine of Zeus at Nemea in the Argolid and at that of Poseidon at the Isthmus of Corinth.

Religious dissent found expression as early as the sixth century B.C., when the poet Xenophanes of Colophon wrote that if animals were to worship gods, they would worship gods with the shape of animals, and complained of the immoral behavior with which the gods were credited in myth. Early philosophical thinkers tended to monotheism, perhaps under the influence of the monotheistic religions of Asia Minor. But persecution for blasphemy or heresy was rare; prosecutions for atheism were grounded on the danger that it might alienate the gods who protected the community, and such prosecutions usually occurred only when the persons prosecuted had given offense in other ways. The Greek gods, unlike some other gods, could take a joke; in the special context of the comedies produced in fifth-century Athens, gods could be made fun of without anyone taking offense. Poets occasionally read the gods, and Zeus in particular, a lecture regarding their injustice in failing to reward good and punish evil.

But after the fifth century, philosophy distanced itself more and more from traditional religion. Plato denounced the immorality of the gods portrayed by Homer and the other poets; revolting against the traditional view that a man proved himself by his ability to benefit his friends and harm his enemies, he created an ethics that had much in common with that of Christianity. He did not wish to suppress the worship of the traditional gods, but they played no part in his philosophy. Aristotle’s ethics had more in common with traditional Greek views than those of Plato, but even to Aristotle the traditional gods meant little more than they would later mean to Epicurus. To highly educated people, philosophy came to take much the kind of place that religion occupied for such people before the 19th century. But the worship of the gods and the observation of their cults continued for 800 years after Plato, and were terminated only by the barbarous Christian emperor Theodosius I, at the end of the fourth century after Christ.