The Historical Library of Diodorus the Sicilian/Book XIV/Preface

Preface
IT is common and natural for every man to be touched to the quick, to hear himself evil spoken of. For even they that are so notoriously wicked that they cannot escape reproaches, yet, if they be told of their faults, are presently in a rage, and do all they can to palliate and cover their crimes with fine-spun excuses. Every one therefore ought to be very careful to avoid the doing of that which is of bad report, especially those that are in high place and power, and advanced above others in dignity. For their actions, by reason of their eminency in the world, being more conspicuous than others, their faults and miscarriages likewise are more obvious. Therefore, let none in such places of power and authority, think to avoid the censures and reproaches, if they are corrupt and unjust in their administration. For should they escape infamy and disgrace during their lives, yet let them be assured, that after times will publish that truth (to the stain of their memory) which was stifled and smothered some time before. Let this therefore startle wicked men to consider, that they leave behind them an ugly representation of themselves, to the view of posterity for ever.

For though those things that follow after death do nothing at all concern us, (as some philosophers have spread abroad among the common people), yet a wicked course of life is far the worse, inasmuch as the remembrance of it is hateful to all posterity. Of which truth, he who seriously considers things related in this book, may find ready at hand most clear and evident examples. For the thirty tyrants of Athens, who by their covetousness and ambition involved their country in dreadful calamities, thereby, in a short time, not only lost their authority, but left behind them an immortal stain and dishonour to their names. And the Lacedæmonians, who had undoubtedly gained the sovereignty of all Greece, lost what they had gained, when they began to oppress their associates and confederates—For the thrones of princes are supported by justice and mercy, but are overturned by cruelty and oppression of their subjects. As we may see in the example of Dionysius the tyrant of Syracuse, who, though he had the smiles of fortune above all the other princes before him, yet plots were formed to entrap him all his life long; so that for fear of being assassinated, he was necessitated to wear an iron breastplate upon his coat, and after his death, became an instance and example of the people's hatred to all succeeding generations. But qwe shall speak of these things in their proper places.

And now we come to those affairs that have a coherence with them before related, only distinguished by differences of time. For in the foregoing books we have treated of things that were done from the sacking of Troy, to the end of the Peloponnesian war, and the Athenian dynasty; which comprehends the space of seven hundred and seventy-nine years. In this we shall add what next follows in order, and begin with the thirty tyrants of Athens, and from thence down to the taking of Rome by the Gauls, wherein is contained the history of eighteen years.