Pericles made this statement as a means to show the difference between Athens and all other civilizations during this era.
This speech, given after one of the first battles of the Peloponnesian War, is trying to rally Athenian citizens. Pericles is trying to elaborate on why the Athenians need to continue this war, as the city-state is one of intellectual superiority. This civilization was known for its academic accomplishments and government system that allowed citizens to decide who ran their government. In discussing all these factors, Pericles is doing his best to show citizens why the preservation of this society is crucial.