It is not possible to found a ...

It is not possible to found a lasting power upon injustice, perjury, and treachery. These may, perhaps, succeed for once, and borrow for awhile, from hope, a gay and flourishing appearance. But time betrays their weakness, and they fall into ruin of themselves. For, as in structures of every kind, the lower parts should have the greatest firmness--so the grounds and principles of actions should be just and true.
 Demosthenes

Quotes from the same author

Small opportunities are often the beginning of great enterprises.
 Demosthenes
The more able a man is, if he make ill use of his abilities, the more dangerous will he be to the commonwealth.
 Demosthenes
It is the natural disposition of all men to listen with pleasure to abuse and slander of their neighbour, and to hear with impatience those who utter praises of themselves.
 Demosthenes
Excessive dealings with tyrants are not good for the security of free states.
 Demosthenes
Close alliances with despots are never safe for free states.
 Demosthenes