POSEIDON (ΠΟΣΕΙΔΏΝ). - God of the waters, whose prerogative seems to be symbolized by the root common to his name (πόσις, ποντίζω, πάνταμαις; v. H. L. Ahrens, Über den Namen des Poseidon, in Philologus, 23 [1866], p. 1 ff.).
Originally his dominion embraced the entire earth, which was subject to his power manifesting itself in seismic shocks (ἐννοσίγαιος, ἐνοσίγθων γαύργος). One among the many testimonies that confirm this character of his as earth-shaker is the sanctuary that, under the appellation of ἀσφάλιος, the Rhodians erected to him on a new islet formed near Thera, one of the Sporades, following a volcanic eruption (Strabo, I, 3, 16; ἀσφάλιος = terram stabilens, according to Macrobius, Sat., I, 17, 22). Elsewhere, as at Troezen, he was considered a god of vegetation (φυτάλμιος: Plutarch, Thes., 6). Going back to the primitive conception of an earth god, P. was worshipped principally in Thessaly, in Boeotia (Etymol. mag., 547, 16) and in the Peloponnese (Diodorus Sic., XV, 40). Traces of fetishism are found in Arcadia, at Thelpusa (Pausanias, VIII, 25, 4, 10) and at Phigalia (ibid., VIII, 5, 5; 42, 4) where, in connection with the cult of Demeter Melaina, the God appears in the form of a horse (P. Hippios at Lykosura, Mantinea, etc. cf. Iliad, XXIII, 584; Hymni Homerici, 22, v. 5).
It is probable that the Thessalian and Boeotian colonists, who emigrated under the pressure of new invasions to the coasts of Asia Minor, modified the archaic prerogative of P. as protector of springs and rivers into that of ruler of the sea. Indeed, with Homer (Iliad, XV, 187 ff.) P. is one of the three sons of Kronos and possesses in the sea the well-defined sphere of his dominion; in later tradition the whole retinue of marine divinities will be attributed to him (spouse of Amphitrite, etc.). His cult was very widespread in the various localities of Greece and Ionia, where temples and sanctuaries were erected to him. Famous was that on the isthmus of Corinth. Already for some time, considered as an indigenous god together with Athena, he was worshipped on the acropolis of Athens as P.-Erechtheus in the temple of the same name (on an older sanctuary ἀρχαῖος νέος; v. W. Judeich Topographie von Athen, Munich 1931, p. 259 ff.). At Rome, under the name of Neptunus, from the Etruscan « nePuns », P. had the same attributes of god of the sea, and in his honor the Neptunalia were celebrated on July 23, made more important after the victory of Actium. As Neptunus equester he was assimilated in a certain way to the Latin god Connus. An altar and a temple of Neptune stood near the Circus Flaminius (Livy, XXVIII, 11, 4; Pliny, Nat. hist., XXXVI, 26; CIL, VI, 8423). Classical art for the most part depicts P. as a man standing in his full maturity with the attributes of the trident and the dolphin.
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Lanfranco Fiore