[usgroup]

Agrippa's trilemma, used as a reductio in your argument. Unfortunately, it applies to pretty much all claim to knowledge not just the case you're using it in.

[PavlovsCat]

I'm not "using" anything, I asked something.

> how can others give you confirmation, if they in turn get their truth and meaning from the outside?

When someone says something like "we get truth and meaning from the outside", I think it's a fair question.