If he does yield fresh information, and if that is known to any living mind, he and his intelligence may have been wired on from that mind.

His only chance is to communicate facts which are proved to be true, facts which nobody living knew before.

Now it is next to impossible to demonstrate that the facts communicated were absolutely unknown to everybody.
Far, however, from conveying unknown intelligence, most ghosts convey none at all, and appear to have no purpose whatever.
It will be observed that there was no traceable reason why the girl with a scar should appear to Mr.G., or the soldier and suppliant to Mrs.M., or Lieutenant B.to General Barker.

The appearances came in a vague, casual, aimless way, just as the living and healthy clergyman appeared to the diplomatist.

On St.Augustine's theory the dead persons who appeared may have known no more about the matter than did the living clergyman.