Although Wissowa treated the categories of "indigetes" and "novensiles" as a fundamental way to classify Roman gods, the distinction is hard to maintain; many scholars reject it. Arnaldo Momigliano pointed out that no ancient text poses "novensiles" and "indigetes" as a dichotomy, and that the etymology of "novensides" is far from settled. In his treatise on orthography, the 4th-century philosopher Marius Victorinus regarded the spellings "novensiles" and "novensides" as a simple phonetic alteration of "l" and "d", characteristic of the Sabine language. Some ancient sources say the "novensiles" are nine in number, leading to both ancient and modern identifications with other divine collectives numbering nine, such as the nine Etruscan deities empowered to wield thunder or with the Muses. The name is thus sometimes spelled Novemsiles or Novemsides.