Think about what you typed for a second. How does one prove existence?<quoted text>
If it is not possible to prove he doesnt exist, how on Earth is it then possible to prove that he does?
Think of something like Bigfoot. What would be proof enough to you that Bigfoot exists? Some country bumpkin saw it while drinking beer after beating his wife? Nah. Not proof. But suppose you find a carcass? Or a live animal? That is proof enough.
Now how about dinosaurs. Mankind did not knkw about these beasts until recently. Yet, we know they existed. How? Fossil evidence. We found bones (fossils are not technically bones, but that is another topic). We find a skeletal structure so completely different than anything that exist today. Radiometric dating puts it at say, 100 million years old. So we know that magnificent beasts roamed the earth long, long before we lever existed.
What shall it be for a deity? If it is a book god, test it to miracles that is aimed it has performed. Make a Christian prophet part the Red Sea, or something like that