InGreek mythology,Hesperus (/ˈhɛspərəs/;Ancient Greek:Ἕσπερος,romanized: Hésperos) is theEvening Star, the planetVenus in the evening. A son of the dawn goddessEos (RomanAurora), he is the half-brother of her other son,Phosphorus (also called Eosphorus; the "Morning Star"). Hesperus' Roman equivalent isVesper (cf. "evening", "supper", "evening star", "west"[1]). By one account, Hesperus' father wasCephalus, a mortal, while Phosphorus was the star godAstraeus. Other sources, however, state that Hesperus was the brother ofAtlas, and thus the son ofIapetus.[2]
Hesperus is the personification of the "evening star", the planetVenus in the evening. His name is sometimes conflated with the names for his brother, the personification of the planet as the "morning star" Eosphorus (GreekἘωσφόρος, "bearer of dawn") orPhosphorus (Ancient Greek:Φωσφόρος, "bearer of light", often translated as "Lucifer" in Latin), since they are all personifications of the same planet Venus. "Heosphoros" in the GreekSeptuagint and "Lucifer" inJerome's LatinVulgate were used to translate the Hebrew "Helel" (Venus as the brilliant, bright or shining one), "son ofShahar (Dawn)" in the Hebrew version ofIsaiah 14:12.
Eosphorus/Hesperus was said to be the father ofCeyx[3] andDaedalion.[4] In some sources, he is also said to be the father of theHesperides.[5]
Maurus Servius Honoratus, in his commentaries onVirgil'sEclogues, mentions that Hesperus inhabitedMount Oeta inThessaly and that there he had loved the youngHymenaeus, son ofDionysus andAriadne. Servius makes no distinction between the Evening Star and the Morning Star, calling them both Hesperus and the Lucifer ofIda.[6]
In thephilosophy of language, "Hesperus is Phosphorus" is a famous sentence in relation to thesemantics ofproper names.Gottlob Frege used the terms "the evening star" (der Abendstern) and "the morning star" (der Morgenstern) to illustrate his distinction betweensense and reference, and subsequent philosophers changed the example to "Hesperus is Phosphorus" so that it utilized proper names.Saul Kripke used the sentence to posit that the knowledge of something necessary (in this case the identity of Hesperus and Phosphorus) could be empirical rather than knowablea priori.