Plutarch Demosthenes 3

[1] Therefore, in this fifth book ¹ of my Parallel Lives, where I write about Demosthenes and Cicero, I shall examine their actions and their political careers to see how their natures and dispositions compare with one another, but I shall make no critical comparison of their speeches, nor try to show which was the more agreeable or the more powerful orator.

[2] as Ion says, a maxim which Caecilius, who goes to excess in everything, forgot when he boldly ventured to put forth a comparison of Demosthenes and Cicero. But really it is possible that, if the Know thyself of the oracle ² were an easy thing for every man, it would not be held to be a divine injunction.
  In the case of Demosthenes and Cicero, then, it would seem that the Deity originally fashioned them on the same plan, implanting in their natures many similarities, such as their love of distinction, their love of freedom in their political activities, and their lack of courage for wars and dangers, and uniting in them also many similarities of fortune.

[3] For in my opinion two other orators could not be found who, from small and obscure beginnings, became great and powerful; who came into conflict with kings and tyrants; who lost each a daughter; who were banished from their native cities and returned with honour; and who, after taking to flight again and being captured by their enemies, ended their lives as soon as their countrymen ceased to be free.

[4] So that, if there should be a competition between nature and fortune, as between artists, it would be difficult to decide whether the one made the men more alike in their characters, or the other in the circumstances of their lives. But I must speak of the more ancient first.