|A general diagram of the dark ages, spanning from the burning of the Library of Alexandra (415), enlightened for a period during the Islamic golden age (c.800-1258AD) (Ѻ) by a number of middle ages geniuses, then darkened, to eventually be re-lighted by the rediscovery of Lucretius (1417). |
In 415, Hypatia was stoned to death (deboundstate), and shortly thereafter the Library of Alexandria was burned and the Roman empire fell (see: rise and fall of civilization); this generally marks the start of the “dark ages”.
From c.1100 to 1453, there was a “middle ages” (see: middle ages geniuses), amid which there was a short “golden age” of middle eastern genius brightness.
In c.1367, Petrarch, after discovering the works of Cicero, and others sharp thinkers of antiquity, introduced, supposedly, the concept of the dark ages. 
In 1562, the works of Sextus Empiricus were published for the first time, in post dark age era, therein fostering the Renaissance.
The following are related quotes:
“Amidst the errors there shone forth men of genius; no less keen were their eyes, although they were surrounded by darkness and dense gloom.”— Petrarch (1367), Defense Against the Calumnies of an Anonymous Frenchman
“In the dark ages people are best guided by religion, as in a pitch-black night a blind man is the best guide; he knows the roads and paths better than a man who can see. When daylight comes, however, it is foolish to use blind, old men as guides.”— Heinrich Heine (c.1830), Thoughts and Ideas 
“When, towards the end of the fifth century, the Roman empire was broken up, there followed, as is well known, a long period of ignorance and of crime, in which even the ablest minds were immersed in the grossest superstitions. During these, which are rightly called the dark ages, the clergy were supreme: they ruled the consciences of the most despotic sovereigns, and they were respected as men of vast learning, because they alone were able to read and write. Such was the degradation of the European intellect for about five hundred years, during which the credulity of men reached a height unparalleled in the annals of ignorance.”— Henry Buckle (1856), History of Civilization, Volume One (pg. 440) 
“While some people think we have come out of the dark ages, I would intuit that we are still residing in Plato’s cave.”— Libb Thims (2016), “mental note reflection”, upon looking at the new revision #1851 of the Hmolpedia main page, after receiving the full 10-volume print set, and marinating in the jump from the Goethe-Schiller dialogue (1799) to the Beg view (1987) to the visual of the print set, with the de Donder view (1936) of the relation between affinity and free energy shown on the cover, repeated ten times, 3:37PM CST Mar 28
1. Buckle, Henry. (1857). History of Civilization, Volume One. Appleton, 1862.
2. Mommsen, Theodore E. (1942). “Petrarch's Conception of the 'Dark Ages'”, Speculum, 17.2:226–42, Apr.
3. Thims, Libb. (2019). Human Chemical Thermodynamics: Chemical Thermodynamics Applied to the Humanities – Sociology, Economics, History, Philosophy, Ethics, Government, Politics, Business, Jurisprudence, Religion, Relationships, Warfare, and Meaning (pdf) (pg. 27). Publisher.
4. (a) Heine, Heinrich. (c.1830). Thoughts and Ideas, Volume Ten (Gedanken und Einfalle, Volume Ten). Publisher.
(b) Hecht, Jennifer M. (2003). Doubt: A History: The Great Doubters and Their Legacy of Innovation from Socrates and Jesus to Thomas (pg. 376). HarperOne.
● Dark ages – Wikipedia.
● Dark ages (historiography) – Wikipedia.