Every now and then I’m asked what sort of evidence would convince me of the existence of God. This is a tough question, and was recently put into relief for me by a Rationally Speaking podcast. There is a fundamental difficulty in finding evidence for God by virtue of how God is defined.
The problem is that most of the substantive parts of the definition of God are natural attributes that other beings also have. God is said, by some, to have a personality. In other words, he is capable of love, trust, sorrow, etc. But these are also human qualities, meaning that any evidence involving these qualities may always be the result of human action, not divine action.
What makes God unique from anything else we know? Perhaps he is omnipotent and omniscient. But how could we be sure of this from observation? In other words, how can we tell if an observation can only be explained by an all-knowing being rather than a being who simply knows a lot, but not everything? How can we tell if an observation can only be explained by an all-powerful being rather than a being who is simply very powerful, but not infinitely so?
Perhaps God is omnipresent. Once again, though, what sort of evidence would demonstrate the existence of an everywhere-present being rather than a being who is simply in many places at once, but not everywhere?
I suspect that to answer the last three questions satisfactorily, we would ourselves have to be omnipotent, omniscient, and omnipresent, in which case God would be just like us, and we would not be compelled to put him at the center of any religious beliefs.
This boils down, in the end, to the fact that nothing supernatural is well defined. This is because we have no idea how to define it. We live in the natural world, and we have no experience of anything other than the natural world, so the word “supernatural” is really just a place holder for anything we think should have some property that is not compatible with anything we’ve ever observed. This, ultimately, is my reason for thinking that God is purely a concept – an idea. Some very modern, liberal theologians like Karen Armstrong seem to be inclined to agree with me. The difference is that I call this atheism, while they do not.