"I demand proof that what you just told us is true."

"I believe you, General, but the commanders will demand proof."

Yet much of the world still demands proof that I am not an alien being.

And doctors generally demand strong evidence, if not proof, before they radically change a standard therapy.

Yet when I demand proof of these accusations, you offer none.

However, he claimed he'd done nothing wrong and demanded proof that there was any funny business involved.

It would just confirm that she had been right to demand proof.

Hart demanded proof that his son was with the caller.

You are the sort of man who demands proof even when the truth is staring him in the face.

Do you demand proof that I am not a robot?