Si deus si dea

Si deus si dea is an Archaic Latin phrase meaning "whether god or goddess". It was used to address a deity of unknown gender. It was also written sive deus sive dea, sei deus sei dea, or sive mas sive femina ("whether male or female").

The phrase can be found on several ancient monuments. Archaic Roman inscriptions such as this may have been written to protect the identity of the god if Rome were captured by an enemy. The construction was often used when invoking the god of a place (e.g., "Be you god or goddess who reigns over Carthage, grant us..."). Historian Edward Courtney claimed it was "intended to cover all bases as an acknowledgement of the limitations of human knowledge about divine powers".

In 1820, an altar was discovered on the Palatine Hill with an Old Latin inscription,

which can be transliterated into the modern form as

and translated as

The altar was dated as a late Roman Republic restoration of an Archaic original. In the 19th century it was misidentified as a famous altar to Aius Locutius. The real identity of the divinity cannot be known, as it did not specify whether it is a god or a goddess. The praetor Caius Sextius C.f. Calvinus may have restored an earlier altar reading "sei deo sei deivae", or he may have been restoring an altar that had been left to decay, while the god or goddess it was dedicated to had been forgotten.

Close to the site, four inscribed columns were found dating to the Julio-Claudian period. Column A (now missing) read "Marspiter," or "Father Mars" in Archaic Latin. Column B reads "Remureine," which possibly means "In Memory of Remus." Column C reads "anabestas," possibly referring to a goddess named Anabesta, or else to the Greek anabasio ("to go up") and interpreted as a reference to Remus' scaling of the Roman walls. Column D, the longest inscription, reads:

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