In Praise of Doubt by Bertolt Brecht

Praised be doubt! I advise you to greet
Cheerfully and with respect the man
Who tests your word like a bad penny.
I'd like you to be wise and not to give
Your word with too much assurance.

Read history and see
The headlong flight of invincible armies.
Wherever you look
Impregnable strongholds collapse and
Even if the Armada was innumerable as it left port
The returning ships
Could be numbered.

Thus one day a man stood on the unattainable summit
And a ship reached the end of
The endless sea.

O Beautiful the shaking of heads
Over the indisputable truth!
O brave the doctor's cure
Of the incurable patient!

But the most beautiful of all doubts
Is when the downtrodden and despondent
Raise their heads and
Stop believing in the strength
Of their oppressors.

...

There are the thoughtless who never doubt
Their digestion is splendid, their judgment is infallible.
They don't believe in the facts, they believe only in themselves.
When it comes to the point
The facts must go by the board
Their patience with themselves
Is boundless.  To arguments
They listen with the ear of a police spy.

The thoughtless who never doubt
Meet the thoughtful who never act.
They doubt, not in order to come to a decision but
To avoid a decision.  Their heads
They use only for shaking.  With anxious faces
They warn the crews of sinking ships that water is dangerous.
Beneath the murderer's axe
They ask themselves if he isn't human too.
Murmuring something
About the situation not yet being clarified, they go to bed.
Their only action is to vacillate.
Their favourite phrase is: not yet ripe for discussion.

Therefore, if you praise doubt
Do not praise
The doubt which is a form of despair.
What use is the ability to doubt to a man
Who can't make up his mind?
He who is content with too few reasons
May act wrongly
But he who needs too many
Remains inactive under danger.

You are a leader of men, do not forget
That you are that because you doubted other leaders.
So allow the leader
Their right to doubt.