An idea is a greater monument than a cathedral.

In a war of ideas it is people who get killed.

The clash of ideas is the sound of freedom.

Never invest in an idea you can't illustrate with a crayon.

The man with a new idea is a crank until the idea succeeds.

All great ideas are controversial, or have been at one time.

You do not destroy an idea by killing people; you replace it with a better one.

There is one thing stronger than all the armies in the world, and that is an idea whose time has come.

Many ideas grow better when transplanted into another mind than in the one where they sprang up.

Man's mind stretched to a new idea never goes back to its original dimensions.

Daring ideas are like chessmen moved forward; they may be beaten, but they may start a winning game.

When we are exalted by ideas, we do not owe this to Plato, but to the idea, to which also Plato was debtor.

To make ideas effective, we must be able to fire them off. We must put them into action.

Ideas rise with new mornings but never die.

Defeat is a fact and victory can be a fact. If the idea is good, it will survive defeat, it may even survive the victory.

Every man with an idea has at least two or three followers.

Nothing is more dangerous than an idea, when it is the only idea we have.

You can kill a man, but you can't kill an idea.

You can kill a man but you can't kill an idea.

Ideas are born, they struggle, triumph, change, and they are transformed; but is there a dead idea which in the end does not live on, transformed into a broader and clearer goal?