There is nothing more frightful than ignorance in action.

There is nothing worse than aggressive stupidity.

One of the most dangerous things in the universe is an ignorant people with real grievances. That is nowhere near as dangerous, however, as an informed and intelligent society with grievances.

There is nothing more horrifying than stupidity in action.

Nothing is more dangerous than solitude.

Stupidity is far more dangerous than evil, for evil takes a break from time to time, stupidity does not.

Ignorance is fatal.

It is worse still to be ignorant of your ignorance.

Beware of false knowledge; it is more dangerous than ignorance.

There is nothing in the world more harmful than war and more foolish than armament

Stupid people are dangerous.

Where ignorance is our master, there is no possibility of real peace.

Nothing is as dangerous as an ignorant friend; a wise enemy is to be preferred.

We are to regard existence as a raid or great adventure; it is to be judged, therefore, not by what calamities it encounters, but by what flag it follows and what high town it assaults. The most dangerous thing in the world is to be alive; one is always in danger of one's life. But anyone who shrinks from that is a traitor to the great scheme and experiment of being.