Passages in a section of the Iliad, called the Deception of Zeus, suggest the possibility that Homer knew a tradition in which Oceanus and Tethys (rather than Uranus and Gaia, as in Hesiod) were the primeval parents of the gods. Twice Homer has Hera describe the pair as "Oceanus, from whom the gods are sprung, and mother Tethys". According to M. L. West, these lines suggests a myth in which Oceanus and Tethys are the "first parents of the whole race of gods." However, as Timothy Gantz points out, "mother" could simply refer to the fact that Tethys was Hera's foster mother for a time, as Hera tells us in the lines immediately following, while the reference to Oceanus as the genesis of the gods "might be simply a formulaic epithet indicating the numberless rivers and springs descended from Okeanos" (compare with Iliad 21.195–197). But, in a later Iliad passage, Hypnos also describes Oceanus as "genesis for all", which, according to Gantz, is hard to understand as meaning other than that, for Homer, Oceanus was the father of the Titans.
Plato, in his Timaeus, provides a genealogy (probably Orphic) which perhaps reflected an attempt to reconcile this apparent divergence between Homer and Hesiod, in which Uranus and Gaia are the parents of Oceanus and Tethys, and Oceanus and Tethys are the parents of Cronus and Rhea and the other Titans, as well as Phorcys. In his Cratylus, Plato quotes Orpheus as saying that Oceanus and Tethys were "the first to marry", possibly also reflecting an Orphic theogony in which Oceanus and Tethys—rather than Uranus and Gaia—were the primeval parents. Plato's apparent inclusion of Phorkys as a Titan (being the brother of Cronus and Rhea), and the mythographer Apollodorus's inclusion of Dione, the mother of Aphrodite by Zeus, as a thirteenth Titan, suggests an Orphic tradition in which Hesiod's twelve Titans were the offspring of Oceanus and Tethys, with Phorkys and Dione taking the place of Oceanus and Tethys.
Tethys played no active part in Greek mythology. The only early story concerning Tethys is what Homer has Hera briefly relate in the Iliad’s Deception of Zeus passage. There, Hera says that when Zeus was in the process of deposing Cronus, she was given by her mother Rhea to Tethys and Oceanus for safekeeping and that they "lovingly nursed and cherished me in their halls". Hera relates this while dissembling that she is on her way to visit Oceanus and Tethys in the hopes of reconciling her foster parents, who are angry with each other and are no longer having sexual relations.
Originally Oceanus' consort, at a later time Tethys came to be identified with the sea, and in Hellenistic and Roman poetry Tethys' name came to be used as a poetic term for the sea.
The only other story involving Tethys is an apparently late astral myth concerning the polar constellation Ursa Major (the Great Bear), which was thought to represent the catasterism of Callisto who was transformed into a bear and placed by Zeus among the stars. The myth explains why the constellation never sets below the horizon, saying that since Callisto had been Zeus's lover, she was forbidden by Tethys from "touching Ocean's deep" out of concern for her foster-child Hera, Zeus's jealous wife.
Tethys was sometimes confused with another sea goddess, the sea-nymph Thetis, wife of Peleus and mother of Achilles.
Tethys as Tiamat
M. L. West detects in the Iliad's Deception of Zeus passage an allusion to a possible archaic myth "according to which [Tethys] was the mother of the gods, long estranged from her husband," speculating that the estrangement might refer to a separation of "the upper and lower waters ... corresponding to that of heaven and earth," which parallels the story of "Apsū and Tiamat in the Babylonian cosmology, the male and female waters, which were originally united (En. El. I. 1 ff.)," but that, "By Hesiod's time the myth may have been almost forgotten and Tethys remembered only as the name of Oceanus' wife." This possible correspondence between Oceanus and Tethys, and Apsū and Tiamat has been noticed by several authors, with Tethys' name possibly having been derived from that of Tiamat.
Representations of Tethys before the Roman period are rare.
Tethys appears, identified by inscription (ΘΕΘΥΣ), as part of an illustration of the wedding of Peleus and Thetis on the early sixth-century BC Atticblack-figure "Erskine" dinos by Sophilos (British Museum 1971.111–1.1). Accompanied by Eileithyia, the goddess of childbirth, Tethys follows close behind Oceanus at the end of a procession of gods invited to the wedding. Tethys is also conjectured to be represented in a similar illustration of the wedding of Peleus and Thetis depicted on the early sixth-century BC Attic black-figure François Vase (Florence 4209). Tethys probably also appeared as one of the gods fighting the Giants in the Gigantomachy frieze of the second-century BC Pergamon Altar. Only fragments of the figure remain: a part of a chiton below Oceanus' left arm and a hand clutching a large tree branch visible behind Oceanus' head.
During the second to fourth centuries AD, Tethys—sometimes with Oceanus, sometimes alone—became a relatively frequent feature of mosaics decorating baths, pools, and triclinia in the Greek East, particularly in Antioch and its suburbs. Her identifying attributes are wings sprouting from her forehead, a rudder/oar, and a ketos, a creature from Greek mythology with the head of a dragon and the body of a snake. The earliest of these mosaics, identified as Tethys, decorated a triclinium overlooking a pool, excavated from the House of the Calendar in Antioch, dated to shortly after AD 115 (Hatay Archaeology Museum 850). Tethys, reclining on the left, with Oceanus reclining on the right, has long hair, a winged forehead, and is nude to the waist with draped legs. A ketos twines around her raised right arm. Other mosaics of Tethys with Oceanus include Hatay Archaeology Museum 1013 (from the House of Menander, Daphne), Hatay Archaeology Museum 9095, and Baltimore Museum of Art 1937.126 (from the House of the Boat of Psyches: triclinium).
In other mosaics, Tethys appears without Oceanus. One of these is a fourth-century AD mosaic from a pool (probably a public bath) found at Antioch, now installed in Boston, Massachusetts at the Harvard Business School's Morgan Hall and formerly at Dumbarton Oaks, Washington, D.C. (Dumbarton Oaks 76.43). Besides the Sophilos dinos, this is the only other representation of Tethys identified by inscription. Here Tethys, with a winged forehead, rises from the sea bare-shouldered, with long dark hair parted in the middle. A golden rudder rests against her right shoulder. Others include Hatay Archaeology Museum 9097, Shahba Museum (in situ), Baltimore Museum of Art 1937.118 (from the House of the Boat of Psyches: Room six), and Memorial Art Gallery 42.2.
Toward the end of the period represented by these mosaics, Tethys' iconography appears to merge with that of another sea goddess Thalassa, the Greek personification of the sea (thalassa being the Greek word for the sea). Such a transformation would be consistent with the frequent use of Tethys' name as a poetic reference to the sea in Roman poetry (see above).
^Hesiod, Theogony 126 ff.; Caldwell, p. 35 line 126-128. Compare with Diodorus Siculus, 5.66.1–3, which says that the Titans (including Tethys) "were born, as certain writers of myths relate, of Uranus and Gê, but according to others, of one of the Curetes and Titaea, from whom as their mother they derive the name".
^Apollodorus adds Dione to this list, while Diodorus Siculus leaves out Theia.
^One of the Oceanid daughters of Oceanus and Tethys, at Hesiod, Theogony 351. However, according to Apollodorus, 1.2.3, a different Oceanid, Asia was the mother, by Iapetus, of Atlas, Menoetius, Prometheus, and Epimetheus.
^Although usually, as here, the daughter of Hyperion and Theia, in the Homeric Hymn to Hermes (4), 99–100, Selene is instead made the daughter of Pallas the son of Megamedes.
^Gantz, p. 28: "For Tethys, there are no myths at all, save for Hera’s comment in the ‘’Iliad’’ that she was given by Rhea to Tethys to raise when Zeus was deposing Kronos"; Burkert, p. 92: “Tethys is in no way an active figure in Greek mythology”; West 1997, p. 147: "In early poetry she is merely an inactive mythological figure who lives with Oceanus and has borne his children."
^West 1966, p. 204 136. Τῃθύν; West 1997, p. 147; Hard, p. 40; Matthews, p. 199. According to Matthews the "metonymy 'Tethys' = 'sea' seems to occur first in Hellenistic poetry", see for example Lycophron, Alexandria 1069 1069 (Mair, pp. 582–583)), becoming a frequent occurrence in Latin poetry, for example appearing nine times in Lucan.
^For a discussion of Tethy's iconography see Jentel, pp. 1193–1195.
^LIMC 6487 (Tethys I (S) 1); Beazley Archive 350099; Avi 4748; Gantz, pp. 28, 229–230; Burkert, p. 202; Williams, pp. 27 fig. 34, 29, 31–32; Perseus: London 1971.11–1.1 (Vase); British Museum 1971,1101.1.
^LIMC 1602 (Okeanos 3); Beazley Archive 300000; Perseus Florence 4209 (Vase). The identification as Tethys is accepted by Beazley, p. 27, and Gantz, p. 28, but found "unconvincing" by Carpenter p. 6. This vase is unremarked upon by Jentel, who says that the Sophilos dinos Tethys (LIMC Tethys I (S) 1) is the "seule representation de [Tethys] à l'époque archaique".
^LIMC 617 (Tethys I (S) 2); Jentel, p. 1195; Queyrel, p. 67; Pollit, p. 96.
^For a discussion of this group of mosaics, see Jentel, 1194–1195, which lists 15 Roman period Tethys mosaics (Tethys I (S) 3–17), and Wages, pp. 119–128. Doro Levi identified the sea goddess in the Antioch mosaics as Thetis, however according to Wages, p. 126, "Neither the inscriptions nor the attributes in this group of mosaics support Doro Levi's identification". See also Kondoleon, p. 152 with p. 153 n. 2, which, in discussing one of these mosaics (Baltimore Museum of Art 1937.118, see below), says that "although the Baltimore goddess does not have any other attributes or label, she is convincingly identified as Tethys" saying further (in the note) that "Levi identified her as Thetis without much evidence, but Wages makes a good argument for identifying her as Tethys". Jentel identifies these mosaics as Tethys, while noting, p. 1195, that "Dès l'Antiquité et encore actuellement, certains auteurs ont confound [Tethys] avec la Néréeid Thetis."
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