It's often claimed the God hypothesis is not empirically or scientifically testable. The idea seems to be that God necessarily transcends the empirical realm, and so his existence cannot be conclusively verified or falsified by reference to it. The most we can have are clues (such as those that prompt the question: "Well, why is the universe so fine-tuned for life, if it wasn't designed that way - by God?" - but even theists admit this is no "proof" of God's existence).
Indeed, God's existence is often said to be beyond the ability of reason to decide. For example:
“Let us say: 'Either God is or he is not.' But to which view shall we be inclined? Reason cannot decide this question." Blaise Pascal.
I don't accept that whether or not God exists is something it is in principle beyond reason, empirical observation, or science to establish, at least not beyond reasonable doubt.
Especially if we conceive of God as the all-powerful and maximally good being of traditional monotheism. Seems to me that hypothesis is straightforwardly empirically falsified.
To see why: take the hypothesis that there's an all-powerful maximally-evil being. That's straightforwardly empirically falsified, surely. There's just way too much good in the world for this to be the creation of such a being. Call that the problem of good. The problem of good surely decisively rules out the evil God hypothesis (notwithstanding all the tricksy moves that might be made to try to salvage it - see my The God of Eth). Which is why everyone dismisses it as silly.
But if the evil God hypothesis is not in principle untestable (and is, in fact, straightforwardly empirically falsified) why should we suppose the all-powerful, maximally good God hypothesis is in principle empirically untestable?
Indeed, seems to me that not only is it testable, it is also straightforwardly empirically falsified - by the problem of evil. Just as the problem of good is decisively rules out an evil God, so the problem of evil decisively rules out the good God.
Or so I argue. See The God of Eth.