Personally I haven’t thought there was one since way back sometime in my mid-teens (and I’m 71 years old now), nor believed in a Heaven, nor in a Hell, nor in anything supernatural at all, and I have no inclination to change. So I’m staying entirely out of answering this, and I won’t be commenting or otherwise on any of the answers. And I’m humbly requesting that other non-believers stay out of it, too, in order to keep from clogging up the point of the question. Because I’d really like to know any and all reasons that anyone who does think there is a God thinks so.

So, to restate it:

Only if you do think there is a God, what makes you think so?