It can't be turtles all the way down, so maybe set theory?

A good question isn't it?

For parallel ideas and situation, take a look at Lincos https://en.wikipedia.org/wiki/Lincos_(artificial_language)

Thank you! I started to think on those lines too thanks to the Carl Sagan's Contact novel. That was the first thing that came to mind.

Now the question is, what if there are "objects" more advanced than others and what if advanced-object sends a message concealing an trojan horse? I think this question was also brought up in the novel/movie too...

I think this is a real life and practical show stopper to develop this concept...

Thanks for the reference. I've been trying to think along these lines.

Wow. Thanks.