Because it goes against the evidence.Why can't you accept that?
You have accepted that a definition does not mean something exists. Yet here you are failing to be able to separate the definition from the existence of that thing.I've already explained that God is already defined, and the instruction was to imagine God does not exist. Outside of using the definition of God in the exercise, I don't know how to imagine a world where God does not exist. And neither do you. Because as the trojan horse concluded, it would be just like the world is now. The world we live in has a definition of God. Any deviation from that is a description of something else. Not God.
You simply can not seem to consider the notion of God simply as a concept, a fiction. You have this a priori assumption that God exists.
I can imagine a world where God exists and a world where God does not exist. Both look identical to the one we're in now - because whether or not God exists in actuality, we do. Thus if God does not happen to actually exist, and all definitions merely apply to a concept (the same way as mentioned with Superman), then we still exist. If God does exist in actuality, then we still also exist.
And this is the distinction between God as concept, and God as an actuality beyond that. Both have the same definition, but only one of those actually exists. Superman is a concept, but Superman is not an actuality beyond that.Ideas and concepts exist, and have profound effects on our lives. If I ask you if you believe in God, you'll say no (after a load of ranglins). But you'll know why you don't believe, because you know what is being asked of you. So God is established in the sense that some people believe in Him, and some don't. So if asked to imagine God, we are asked to imagine God, as we know Him, whether we accept He exists or not.
You can't seem to separate definition from existence, no matter how hard you try to deny otherwise, no matter how much lip-service you seem to give to the contrary.