An Irish precursor of Dante

Civilization, Celtic, in literature; Dante Alighieri, 1265-1321 -- Criticism and interpretation; Fís Adamnáin; Christian literature, Irish -- History and criticism; Heaven -- Christianity -- History of doctrines -- Middle Ages, 600-1500; Hell -- Christianity -- History of doctrines -- Middle Ages, 600-1500; Christian saints -- Ireland; Heaven in literature; Hell in literature