The concept of ‘god’ can mean many different things – or perhaps it can mean anything, given the apparent limitless number of characteristics which various believers assign to their gods. Any time someone asks you why you don’t believe in any gods, make sure you ask them what they mean by ‘god’ in the first place. Chances are, it’s simply not something which requires belief.
In Conversations with Carl Sagan, edited by Tom Head, Carl Sagan says in an interview published in the U.S. Catholic in 1981:
When people ask me after one of my lectures, “Do you believe in God?” I frequently reply by asking what the questioner means by “God.” The term means a lot of different things in a lot of different religions. For some, it’s an outsized, light-skinned male with a long white beard, sitting on a throne somewhere up there in the sky, busily tallying the fall of every sparrow. To others — for example, Baruch Spinoza, and Albert Einstein — God is essentially the sum total of the physical laws which describe the universe. I can’t imagine anyone denying the existence of the laws of nature, but I don’t know of any compelling evidence for the old man in the sky.
In the cosmic context, the very scale of the universe — more than one hundred billion galaxies, each containing more than one hundred billion stars — speaks to us of the inconsequentiality of human events. We see a universe simultaneously very beautiful and very violent. We see a universe that does not exclude a traditional Western or Eastern god, but that does not require either.
The contrast here between the laws of nature and gods is very instructive. People might have legitimately different views on just what the laws of nature are and how they operate, but when you get right down to it no one denies that there are laws of nature and there is very little disagreement on what the basic laws of nature are.
People don’t deny the existence of gravity, for example. Why not? There is just too much that happens every day for which gravity is the most obvious and best explanation. It doesn’t make sense to say that we fall when we trip because invisible fairies push us, or a pencil falls when we drop it because invisible fairies are pushing on it — that if the fairies didn’t exist, we and our pencils would never hit the ground. Some common force is acting here on us and the pencils; gravity not only explains what happens, but allows us to predict future events with great accuracy. The fairy theory doesn’t.
We encounter a very different situation when we come to alleged gods, however, People claim the existence of all sorts of mutually exclusive deities, but they can never point to some basic, recurring aspect of the universe which absolutely compels belief in some sort of god, even if it’s not theirs. What is going on out there or around us which only makes sense in the context of some god? More importantly, what does this “god theory” predict with any accuracy, such that we can test it and discover that it’s a reliable, accurate explanation for events?
Nothing like this exists. Unequivocal evidence compels belief in something like gravity acting on us and everything around us; absolutely no evidence comes anywhere close to compelling belief on anything like a god. Perhaps the facts about the universe don’t absolutely exclude the possibility of some versions of gods from existing, but there’s certainly nothing about the universe which suggests that the existence of any gods is very likely.