Of course, modern historians would generally leave out their personal beliefs, which is a form of passing judgment upon the events and people about which the historian is reporting. The work of Herodotus is reported to have been recited at festivals, where prizes were awarded, as for example, during the games at Olympia. Herodotus views history as a source of moral lessons, with conflicts and wars as misfortunes flowing from initial acts of injustice perpetuated through cycles of revenge. In contrast, Thucydides claims to confine himself to factual reports of contemporary political and military events, based on unambiguous, first-hand, eye-witness accounts, although, unlike Herodotus, he does not reveal his sources. Thucydides views life exclusively as "political" life, and history in terms of "political" history. Conventional moral considerations play no role in his analysis of political events while geographic and ethnographic aspects are omitted or, at best, of secondary importance. Subsequent Greek historians—such as Ctesias, Diodorus, Strabo, Polybius and Plutarch—held up Thucydides's writings as a model of truthful history. Lucian refers to Thucydides as having given Greek historians their "law", requiring them to say "what had been done" (). Greek historians of the fourth century BC accepted that history was political and that contemporary history was the proper domain of a historian. Cicero calls Herodotus the "father of history"; yet the Greek writer Plutarch, in his "Moralia" ("Ethics") denigrated Herodotus, notably calling him a "philobarbaros", a "barbarian lover", to the detriment of the Greeks. Unlike Thucydides, however, these authors all continued to view history as a source of moral lessons, thereby infusing their works with personal biases generally missing from Thucydides' clear-eyed, non-judgmental writings focused on reporting events in a non-biased manner. Due to the loss of the ability to read Greek, Thucydides and Herodotus were largely forgotten during the Middle Ages in Western Europe, although their influence continued in the Byzantine world. In Europe, Herodotus become known and highly respected only in the late-sixteenth and early-seventeenth century as an ethnographer, in part due to the discovery of America, where customs and animals were encountered that were even more surprising than what he had related. During the Reformation, moreover, information about Middle Eastern countries in the "Histories" provided a basis for establishing Biblical chronology as advocated by Isaac Newton.