I am leaving soon and you will forgive me if I speak bluntly.
(he pauses, studying the faces)
The Universe grows smaller every day — and the threat of aggression by any group — anywhere — can no longer be tolerated.
There must be security for all — or no one is secure… This does not mean giving up any freedom except the freedom to act irresponsibly.
Your ancestors knew this when they made laws to govern themselves — and hired policemen to enforce them.
We of the other planets have long accepted this principle.
We have an organization for the mutual protection of all planets — and for the complete elimination of aggression.
A sort of United Nations on the Planetary level…
The test of any such higher authority, of course, is the police force that supports it.
For our policemen, we created a race of robots–
(indicating Gort)
Their function is to patrol the planets — in space ships like this one — and preserve the peace.
In matters of aggression we have given them absolute power over us.
At the first sign of violence they act automatically against the aggressor.
And the penalty for provoking their action is too terrible to risk.
The result is that we live in peace, without arms or armies, secure in the knowledge that we are free from aggression and war — free to pursue more profitable enterprises.
(after a pause)
We do not pretend to have achieved perfection — but we do have a system — and it works.
(with straightforward candor)
I came here to give you the facts.
It is no concern of ours how you run your own planet — but if you threaten to extend your violence, this Earth of yours will be reduced to a burned-out cinder.
Your choice is simple. Join us and live in peace. Or pursue your present course — and face obliteration.
(after a pause)
We will be waiting for your answer.
decision rests with you.

Klaatu, closing speech, “The Day the Earth Stood Still”