Thucydides said this quote

We Greeks believe that a man who takes no part in public affairs is not merely lazy, but good for nothing

~ Thucydides

For the whole earth is the tomb of famous men; not only are they commemorated by columns and inscriptions in their own country, but in foreign lands there dwells also an unwritten memorial of them, graven not on stone but in the hearts of men. Make them your examples, and, esteeming courage to be freedom and freedom to be happiness, do not weigh too nicely the perils of war.[Funeral Oration of Pericles]

~ Thucydides

You know and we know, as practical men that the question of justice arises only between parties equal in strength and that the strong do what they can, and the weak suffer what they must.

~ Thucydides

The absence of romance in my history will, I fear, detract somewhat from its interest, but if it is judged worthy by those inquirers who desire an exact knowledge of the past as an aid to the understanding of the future, which in the course of human things must resemble if it does not reflect it, I shall be content.In fine I have written my work not as an essay with which to win the applause of the moment but as a possession for all time.

~ Thucydides