A god of this character would naturally be worshipped on the mountain-tops, and that these were very frequently consecrated to him is shown by the large number of appellatives derived from the names of mountains. But probably in his earliest Hellenic period the power of Zeus in the natural world was not limited to the sky.
A deity who sent the fertilizing rains would come to be regarded as a god of vegetation, who descended into the earth and whose power worked in the life that wells forth from the earth in plant and tree. Homer calls the god of the lower world Zeus Katach thonios (Iliad, ix. 457), and the title of Zeus Chthonios, which was known to Hesiod, occurred in the worship of Corinth (Hesiod, Works and Days, 456; Pausan. ii. 2, 8).
A glimpse into a very old stratum of Hellenic religion is afforded us by the records of Dodona. A Dodonean liturgy has been preserved which, though framed in the form of an invocation and a dogma, has the force of a spell-prayer—"Zeus was and is and will be, 0 great Zeus : earth gives forth fruits, therefore call on Mother Earth" (Pausan. x. 12, I0). Zeus, the sky-god, is seen here allied to the earth-goddess, of whom his feminine counterpart, Dione (q.v.), may have been the personal form. And it is at Dodona that his association with the oak is of the closest. His prophet-priests, the Selloi, "with unwashed feet, couching on the ground" (Homer, Iliad, xvi. 233), lived about the sacred oak, which may be regarded as the primeval shrine of the Aryan god, and interpreted its oracular voice, which spoke in the rustling of its leaves or the cooing of its doves. Zeus, we may believe, long remained at Dodona such as he was when the Hellenic tribes first brought him down from the Balkans, a high god supreme in heaven and in earth.
We may also believe that in the earliest stages of worship he had already acquired a moral and a social character. The Homeric view of him as the all-father is a high spiritual concept, but one of which many savage religions of our own time are capable. The family, the tribe, the city, the simpler and more complex organisms of the Hellenic polity were specially under his care and direction. In spite of the popular stories of his amours and infidelities, he is the patron-god of the monogamic marriage, and his union with Hera (q.v.) remained the divine type of human wedlock.
He was also the tutelary deity of the larger organization of the phratria; and the altar of Zeus Phratrios was the meeting-point of the phrateres, when they were assembled to consider the legitimacy of the new applicants for admission into their circle (Demosth. Contra Macartatum, 1078, i.).
His religion also came to assist the development of certain legal ideas, for instance, the rights of private or family property in land; he guarded the allotments as Zeus Klarios (Pausan. viii. 53, 9), and the Greek commandment, "thou shalt not remove thy neighbour's landmark," was maintained by Zeus Horios, the god of boundaries, a more personal power than the Latin Iuppiter Terminus (Plato, Laws, 842 E).
His highest political functions were summed up in the title Polieus, a cult-name of legendary antiquity in Athens, and frequent in the Hellenic world.
His consort in his political life was not Hera, but his daughter Athena Polias. He sat in her judgment court Eiri IlaXXablco, where cases of involuntary homicide were tried (Corp. Inser. Attic. iii. 71 and 273). With her he shared the chapel in the council-hall of Athens dedicated to them under the titles of Boulaios and Boulaia, "the inspirers of counsel," by which they were worshipped in many parts of Greece (Antiphon vi. p. 789 ; Pausan. i. 3. 5; cf. Corp. Inser. Attic. iii. 683). The political assembly and the law court were consecrated to Zeus Agoraios, and being the eternal source of justice he might be invoked as Dikaiosunos "The Just." As the god who brought the people under one government he might be worshipped as Pandemos (Corp. laser. Attic. iii. 7) ; as the deity of the whole of Hellas, he became Panhellenios, per haps about the time of the Persian wars, when thanksgiving for the victory took the form of dedications and sacrifice to "Zeus the Liberator" Eleutherios (Simonides, Frag. 140 [Bergk] ; Strab. Finally, in the formulae adopted for the public oath, where many deities were invoked, the name of Zeus was the master word.