How the Irish Saved Civilization: The Untold Story of Ireland's Heroic Role from the Fall of Rome to the Rise of Medieval Europe

Cahill’s explanation of the Roman Empire’s demise draws heavily on Gibbon’s six-volume tome that was published in the mid-1700s CE. Gibbon argues that Rome fell when it became vulnerable to “barbarian” hordes. The Roman Empire’s acceptance of Christianity, he claims, made its collapse possible because Roman Christians cared more about the eternal life that St. Augustine of Hippo termed the City of God than about the earthly sphere. This distraction diverted resources away from the Roman state and to the church, thereby weakening the empire internally. The resulting internal decay made Rome vulnerable to external conquests. Modern historians largely discredit Gibbon, whose work reflects Enlightenment skepticism about religion and is a product of his cultural milieu.

Though Cahill argues that Christianity did not cause Rome’s fall, since it was already declining as a polytheistic society, he adheres to the view that “barbarians” are to blame for Rome’s final disintegration. This perspective neatly divides the classical Roman world from the medieval one. However, most historians assert that this partitioning is oversimplified, and reject the characterization of Germanic and Celtic peoples as “uncivilized” or “barbaric.”

The Irish were different from the Romans in many ways, but Cahill shows that those differences do not equate to inferiority. In fact, he highlights the richness of pre-Christian Irish culture in subsequent chapters.

Cahill’s desire to contrast Rome with the cultures he classifies as violent and ignorant ignores Roman society’s consistent violence and the reality that the empire was built through warfare. For example, Roman generals were permitted to celebrate a triumph only after slaughtering a minimum of 5,000 people on the battlefield. Rome’s fall, Cahill claims, gave way to an unenlightened early medieval world dominated by "inferior" Germanic overlords; this outdated view perpetuates the debunked myth of the Middle Ages as the “Dark Ages.”

Cahill echoes Gibbon’s sentiments in his argument that the loss of most classical knowledge resulted in a “new world” that was fully distinct from Rome. Nevertheless, historian Chris Wickham argued in Early Medieval Italy, which was published over a decade before Cahill’s book, that there was a degree of continuity between the late Roman Empire and the Germanic kingdoms that replaced it.