In Greek mythology, Hesperus (Greek Ἓσπερος Hesperos) (Roman equivalent: Vesper cf. "evening", "supper", "evening star", "west), the Evening Star is the son of the dawn goddess Eos (Roman equivalent: Aurora) and brother of Eosphorus (Ηωσφόρος Eosphoros "dawn-bearer"; also Φωσφόρος Phosphorus, Lucifer "light-bearer", Iubar), the Morning Star. Hesperus' father was Cephalus, a mortal, while Eosphoros' was the star god Astraios.
Hesperus (Greek Hesperos) is the personification of the "evening star", the planet Venus
in the evening. His name is sometimes conflated with the names for his brother the personification of the planet as the "morning star" Eosphorus (Greek Ἐωσφόρος, "bearer of dawn") or Phosphorus
: Φωσφόρος, "bearer of light", often translated as "Lucifer
" in Latin), since they are all personifications of the same planet Venus. "Heosphoros" in the Greek LXX Septuagint
and "Lucifer" in Jerome
's Latin Vulgate
were used to translate the Hebrew "Helel" (Venus as the brilliant, bright or shining one), "son of Shahar (Dawn)" in the Hebrew version of Isaiah
When named thus by the early Greeks, it was thought that Eosphorus (Venus in the morning) and Hesperos (Venus in the evening) were two different celestial objects. The Greeks later accepted the Babylonian view that the two were the same, and the Babylonian identification of the planets with the Great Gods, and dedicated the "wandering star" (planet) to Aphrodite (Roman Venus), as the equivalent of Ishtar.
Eosphorus/Hesperus was said to be the father of Ceyx and Daedalion. In some sources, he is also said to be the father of the Hesperides.
"Hesperus is Phosphorus"
"Hesperus is Phosphorus" is a famous sentence in the philosophy of language
(see, e.g., proper name
). Gottlob Frege
used the terms "Hesperus" and "Phosphorus" to illustrate his distinction between sense and reference
. Saul Kripke
used the sentence to demonstrate that the knowledge of something necessary (in this case the identity of Hesperus and Phosphorus) could be discoverable rather than known a priori