History of the Peloponnesian War

Being incapable, however, through the number of those who had votes, to join together and defend themselves, the allies were reduced to slavery, except ourselves and the Chians; but we joined their enterprises as independent, forsooth, and free-in name. And now we had no longer in the Athenians such leaders as we could trust, having before us the examples that were already given:

for it was not likely that they should reduce to subjection those whom they had taken into treaty along with us, and not do the same to the rest, if ever they had the power.

"If indeed we had all been still independent, they might have been better trusted by us not to attempt any innovation: but having the majority subject to them, while they associated with us on terms of equality; and comparing the submission of the greater part with our alone being treated as equals, they would naturally brook it the worse; especially as they were themselves growing more powerful than ever, and we more destitute. But equality of fear is the only sure basis of an alliance;

for then the party that wishes to commit any offence is deterred by the knowledge that he would not attempt it with any advantage on his side.