In his pioneering study of the medieval Irish evidence for Celtic mythology, published in 1884, Henri d’Arbois de Jubainville wrote that ‘in the divine world of Ireland, we find two groups knit together by the closest ties of relationship, and yet at war one with the other’: these are, on the one hand, the Túatha Dé Donann (‘Tribes of the Goddess Donann’) or Túatha Dé (‘Tribes of the Gods’), the medieval reflections of the deities of the pre-Christian Irish; and, on the other, a race of beings called Fomoiri (singular Fomoir), whom Arbois de Jubainville described as ‘a mythical group corresponding to the Indian Asura and the Greek Titans’. The latter are ‘gods of Death, of Evil, and of Night’, in contrast to the Túatha Dé, whom he called ‘gods of Day, of Righteousness, and of Life’. In 1940, Marie-Louise Sjoestedt reaffirmed this view, likening the Fomoiri to ‘the forces of chaos: eternally “latent”, and enemies of all Cosmos’; and essentially the same idea is apparent in Proinsias Mac Cana's Celtic Mythology three decades later, where the Fomoiri are described as a ‘race of demonic beings’, and as ‘demonic powers’ who ‘wage a continual struggle against the gods’.