is is, exist exist, to be to be

The purpose of existence is a tautology. Existence is the point of existence. Just saying "Existence is..." is like grammatically saying "Exist exists".

Would you worry a tautology like a rotten tooth? Would you scratch at it like a bad rash?

I don't know why people worry about redefining tautologies as if there is some reason to worry about making tautologies not tautologies. Faith is a fine invention when people can see, and all. Microscopes are nice. Science is your friend. This is all an ouroboros with an amazing complexity of the links of the chain. People are the most important part of science, for it's useless to experiment when no one else can recreate the results in a second laboratory.

Write papers. Publish them. Communicate.