John Scottus Eriugena was the most original synthetic thinker between the time of Augustine and that of Thomas Aquinas. He is certainly the greatest Irish philosopher of all time. In recognition of this preeminent status, an idealized portrait of Eriugena graces the five-pound note of the Republic of Ireland. But close attention of the kind paid to other major medieval thinkers has, in general, rarely been paid to Eriugena, and much of his work remains inaccessible to readers of English. The reasons for this neglect are three: the difficult and complex character of his thought has appealed to only the more dedicated students of medieval philosophy; his influence on medieval thought has seemed slight; and his major work was less than orthodox. Some nineteenth-century scholars turned to the study of Eriugena precisely for these reasons, seeing in him a lonely and misunderstood figure. They characterized him as a...