Titus Livius, From the Foundation of the City 31
The Aitolians, the Akarnanians, the Macedonians, men of the same speech, are united or disunited by trivial causes that arise from time to time; with aliens, with barbarians, all Greeks wage and will wage eternal war; for they are enemies by the will of nature, which is eternal, and not from reasons that change from day to day.