the revolving Heavens (Caelum). The semina rerum ("seeds" of things that exist physically) come from Caelum and are the elements which create the world. The divine spatial abstraction Caelum is a synonym for Olympus as a metaphorical heavenly abode of the divine, both identified with and distinguished from the mountain in ancient Greece named as the home of the gods. Varro says that the Greeks call Caelum (or Caelus) "Olympus." As a representation of space, Caelum is one of the components of the mundus, the "world" or cosmos, along with terra (earth), mare (sea), and aer (air). In his work on the cosmological systems of antiquity, the Dutch Renaissance humanist Gerardus Vossius deals extensively with Caelus and his duality as both a god and a place that the other gods inhabit. The ante-Nicene Christian writer Lactantius routinely uses the Latin theonyms Caelus, Saturn, and Jupiter to refer to the three divine hypostases of the Neoplatonic school of Plotinus: the First God (Caelus), Intellect (Saturn), and Soul, son of the Intelligible (Jupiter). In art It is generally though not universally agreed that Caelus is depicted on the cuirass of the Augustus of Prima Porta, at the very top above the four horses of the Sun god's quadriga. He is a mature, bearded man who holds a cloak over his head so that it billows in the form of an arch, a conventional sign of deity (velificatio) that "recalls the vault of the firmament." He is balanced and paired with the personification of Earth at the bottom of the cuirass. (These two figures have also been identified as Saturn and the Magna Mater, to represent the new Saturnian "Golden Age" of Augustan ideology.) On an altar of the Lares now held by the Vatican, Caelus in his chariot appears along with Apollo-Sol above the figure of Augustus. Nocturnus and the templum As Caelus Nocturnus, he was the god of the night-time, starry sky. In a passage from Plautus, Nocturnus is regarded as the opposite of Sol, the Sun god. Nocturnus appears in several inscriptions found in Dalmatia and Italy, in the company of other deities who are found also in the cosmological schema of Martianus Capella, based on the Etruscan tradition. In the Etruscan discipline of divination, Caelus Nocturnus was placed in the sunless north opposite Sol to represent the polar extremities of the axis (see cardo). This alignment was fundamental to