History of the Peloponnesian War

Therefore it is on this very account that our city is seldom quiet, but is subject to frequent feuds and conflicts—not so much with the enemy as with itself—and sometimes to tyrannies and wicked oligarchies.

But if you will only follow me, I will try to see to it that never in our time shall any of these things come to pass, persuading you who are the mass of the people, but chastising the men who devise such things, not only when they are caught in the act—as it is difficult to come upon them—but even for what they would but cannot do. For an enemy one must forestall, not only in what he does, but even in his designs, since indeed a man who is not first to safeguard himself will be first to suffer. As to the oligarchs, on the other hand, I shall sometimes expose them, and sometimes watch them, but sometimes also I shall instruct them, for in this way I think I could best deter them from evil-doing.