Only consider what a blunder you would commit in doing as Cleon recommends.
As things are at present, in all the cities the people is your friend, and either does not revolt with the oligarchy, or, if forced to do so, becomes at once the enemy of the insurgents; so that in the war with the hostile city you have the masses on your side.
But if you butcher the people of Mitylene, who had nothing to do with the revolt, and who, as soon as they got arms, of their own motion surrendered the town, first you will commit the crime of killing your benefactors; and next you will play directly into the hands of the higher classes, who when they induce their cities to rise, will immediately have the people on their side, through your having announced in advance the same punishment for those who are guilty and for those who are not.
On the contrary, even if they were guilty, you ought to seem not to notice it, in order to avoid alienating the only class still friendly to us.
In short, I consider it far more useful for the preservation of our empire voluntarily to put up with injustice, than to put to death, however justly, those whom it is our interest to keep alive.
As for Cleon's idea that in punishment the claims of justice and expediency can both be satisfied, facts do not confirm the possibility of such a combination.