Demosthenes

There are all kinds of devices invented for the protection and preservation of countries: defensive barriers, forts, trenches, and the like... But prudent minds have as a natural gift one safeguard which is the common possession of all, and this applies especially to the dealings of democracies. What is this safeguard? Skepticism. This you must preserve. This you must retain. If you can keep this, you need fear no harm.