Things don't have to be testable to be true

[Thumpalumpacus]

Caesar's existence is in fact testable. The fact that you haven't examined the evidence is not a sign of his nonexistence, but your ignorance.

Also interesting is that by your logic you cannot prove the existence of your own "God".

Finally, anyone who thinks that science is not tentative really doesn't understand science and should probably get through high-school at the very least before opining.