一個好的歷史家的來源（source/material) 最好是在事件發生的年代或離那年代不久的歷史學家所寫的. Edward Gibbon 之所以是 the historian of historians 是因為他寫 The History of the Decline and Fall of the Roman Empire 時都根據 Roman historians (such as Tacitus, Suetonius) 所寫的歷史，Roman historians 是用拉丁文寫的。
Churchill 寫 A history of English Speaking People 時有提到他是根據某某的 English translation of Tacitus’s works. (Churchill 有次提到為什麼他的英文特別好，他説當他的同學都在學 Latin and Greek 時，他只在學英文）Julius Caesar 兩度 進軍British Islands,大概是 Jesus 誕生的 50 年前。所以要寫英倫歷史是要牽涉到羅馬歷史的。
Gibbon 懂 Latin, Greek, and French, 因為很多古老歷史的書都用這些語言寫的。
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| The Great Books of the Western Word have 2 books of Gibbon's |
我舉個例子來説明 Gibbon 如何利用 Tacitus and Suetonius 的資料。在説明為什麼Roman Empire 想征服 British islands, 其中一個原因是謠言英倫有「pearl fishery」（珍珠），
（以下是 來自 Gibbon 的 Roman Empire)
The only accession which the Roman Empire received, during the first century of the Christian Aera, was the province of Britain. In this single instance, the successors of Caesar and Augustus were persuaded to follow the example of the former, rather than the precept of the latter. The proximity of its situation to the coast of Gaul 【歐洲大陸本土】seemed to invite their arms; the pleasing though doubtful intelligence of a pearl fishery, attracted their avarice; 6
6 (return) [Caesar himself conceals that ignoble motive; but is mentioned by Suetonius, c. 47. The British Pearls proved, however, of little value, on account of their dark and livid color. Tacitus observers, with reasons, (in Agricola, c. 12,) that it was an inherent defect. “Ego facility’s crediderim, natural margaritas deesee qualm nobis avaritiam.”]
Julius Caesar 自己都有寫下他進攻 Britain 的經過，但是都沒有提到 pearls fishery 之事,堂堂 Caesar emperor 一個，怎麼可以為了區區幾個珍珠 千軍萬馬 飃洋過海 進攻英倫呢，但是歴史學家不會放過他的。
Churchill, in his A History of English Speaking People 也提到 pearls fishery.
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| Churchill's A History of English Speaking People |
To Caesar the Island now presented itself as an integral part of his task of subjugating the Northern barbarians 【只要不是 Romans, 其他的人都是 barbarians, 只要不是漢人，真他的人都是番人，古今中外皆然】to the rule and system of Rome.
The natives, though uncouth, had a certain value as slaves for rougher work on the land, in mines, even about the house. There was talk of a pearl fishery, and also of gold.
由此可知 Gibbon 及 Churchill 都根據同資料, 只是 Gibbon 讀原文（Latin); Churchill 讀英文翻譯。
