In Antony’s letters the understanding of demons is somewhat different [than in Athanasius’ The Life of Antony]: they are not palpable, visible presences; nevertheless they ‘are omnipresent: making the bodies of man their dwelling, they condemn him to lifelong warfare within himself. His hope for deliverance rests with his prayers for God’s compassion (Rubenson, The Letters of Saint Antony: Monasticism and the Making of a Saint, p.140).

–  Tim Vivian, translator, “Introduction” to The Life of Antony, CS202 (2003)