Want proof? Find a single base truth that is true in every context. You can't. It's just that simple.
I'm going to play weenie semantic games with you like a one-time logician because I think you're understating your case by avoiding them. P or not-P. Tautologies are true no matter what, so there surely are truths that are true in every context, they're just useless by virtue of being true in every context. They say nothing about everything, which is the only thing that can be said about everything.