This is a classic philosophical argument that was dispensed with in the middle ages. The usual form of it is "how can you know what infinity is if infinity doesn't exist?" The answer is as simple as "I take the word finite and put the word not in front of it." We are perfectly capable of synthesizing concepts that do not exist in our experience of reality.
>We are perfectly capable of synthesizing concepts that do not exist in our experience of reality.
I am not sure exactly what this means, but I don't think I asserted anything to the contrary.
An automaton or a parrot can place words next to each other without "synthesizing concepts". Can an intelligent being not do that too?
As another application of my original point, "synthesizing concepts" would not mean anything unless it was possible (and I think it is) to not synthesize a concept when a string of symbols is put together.
It's not that we have to have a caring universe to imagine one, it's that we have to at least imagine one in order to say the universe is not caring.
One way to look at the universe we live in is that it seems to be faithful. Every atom follows physical law perfectly, at least we assume. Maybe that's not exactly proven, but it's the conventional faith today, and we certainly can imagine the world otherwise, with lots of miracles.