Well then we have no indication of whether David Irving was a credible historian.

except what Jorg Haider said

Ah but if he is not a credible source than we cannot consider that a true indication of whether he is a credible historian.

well it means there is a suggestion that he is a credible historian, not a credible suggestion but more than no suggestion

I have a credible suggestion, my dad said he saw David Irving lecture once and he was a twat

that sounds more convincing than herr haider's evidence

Is Pliny's dad credible?

relatively

Of course he's a relative, that was obvious from the fact that they're related.

i think he's relatively reliable as a source as far as we are aware there is nothing to suggest he's as unreliable as the other

He probably is. It'd be good to be confident in our levels of awareness however.

He has a third in history from cambridge, I don't know if that makes him credible :|

Nor do I

nor should you

nor should I