I'm happy to follow Descartes' Cogito Ergo Sum - I think Therefore I Am.
The fact that I am thinking is proof enough for me to believe that I exist. Of course, as Old_Geezer says, I don't know that the universe or the rest of you exist. And I don't know what my existnce involves: I may be an alien on Mars, just dreaming about living on a planet called Earth.
But we get along OK by living with probabilities. That evolution explains complex life is extremely probable because it makes sense and there is a mass of evidence to support it. That gods exist is extremely improbable because it makes no sense and there is no evidence to support the idea. If we use our brains we can do without proof.