This is from Thucydides, book 1, section 141. The Athenians have met to decide whether they should, in effect, initiate a war against the Spartans. If they do, they'll have to fight not only the Spartans but the entire alliance of the Peloponnesian League. Pericles says this about the allies of Sparta:
"...they cannot fight a war against a power unlike themselves, so long as they have no central deliberative authority to produce quick, decisive action, when they all have equal votes, though they all come from different nationalities and every one of these is mostly concerned with its own interests -- the usual result of which is that nothing gets done at all, some being particularly anxious to avenge themselves on an enemy, and others no less anxious to avoid coming to any harm themselves. Only after long intervals do they meet together at all, and then they only devote a fraction of their time to their general interests, spending most of it on arranging their own separate affairs. It never occurs to any of them that the apathy of one will damage the interests of all. Instead, each state thinks that the responsibility for its future belongs to someone else, and so, while everyone has the same idea privately, no one notices that from a general point of view things are going downhill."
There seems to be a general view amongst professional historians that the speeches in Thucydides are not to be trusted, particularly the speeches known as the Melian Dialogue, which could have taught Machiavelli a thing or two about realpolitik. (In fact, they probably did.)
Unlearned me goes against the learned opinion on this. I find it difficult to read something like the above without nodding my head and thinking, yep, that came from an experienced and cynical politician who knew what he was talking about.