And is there any way to prove it, if he did?

There is, of course, no way to prove the cause and effect here.

The only way to prove that to him would be to find a live one, of course.

There's no way to prove she was right or wrong.

There was no way to prove I'd been on the river.

The best way to prove she's tough is to be herself.

But on the other hand, it was certainly the best way to prove himself.

The only way to prove any of it is to get my hands on him.

That's the only way to prove which system is better in the long run.

Let him go out of his way to prove a point.