History of the Peloponnesian War

When the Mantineans had revolted, the rest of the Peloponnese also was thrown into commotion, with the idea that they too ought to do the same; as they thought that they had changed sides through knowing more than the rest. At the same time they were angry with the Lacedaemonians, both on other grounds, and because it had been mentioned in the treaty with Athens, that it should be consistent with their oaths to add to it, or take from it, whatever might seem fit to both states, the Lacedaemonians and Athenians.

For it was this clause, above all, that caused the excitement in the Peloponnese, and set them on suspecting that the Lacedaemonians, in concert with the Athenians, might wish to reduce them to slavery: for it was only just, they thought, that the alteration should have been referred to all the allies.