Dark Ages

Without Christianity, the Dark Ages would have truly been dark.

I recommend getting a better source.

The fountainhead of the theory that the ascension of Christianity to a position of privilege among the religions of the Roman empire was one of the major causes of the fall of that empire is the book The History of the Decline and Fall of the Roman Empire by Edward Gibbon. It was published in 6 volumes over the years from 1776 - 1789.

Though Gibbon's theory of Christianity's contribution to the fall of Rome was widely criticized at the time of its publication, it gained in popularity among serious historians due to its groundbreaking use of modernist techniques, such as the use of primary sources. As the enlightenment progressed, popular outrage gave way to an acceptance of his theory, and his books became both the standard in the field among historians and a popular success among the reading public.

Historians of late antiquity began to seriously question Gibbon's theory some decades ago. However, the long-running popularity of his books has caused his theory to become entrenched in the popular consciousness to such a degree that it has proven difficult to dislodge.