But he would not believe it to be true without proof.

The woman would not believe the sky was blue without proof.

I would not have believed such a thing without proof.

Without proof I should really lay the idea to rest.

Without such proof he'll have to pay the back tax, plus interest.

The boys around the office would never believe it without proof.

After his own experience he could not accept anything here without proof.

He will not do anything that is public and direct without proof.

In a 1954 paper Little's law was assumed true and used without proof.

And it's just not fair that those things can be said without proof.