Necessary Thing

[Ignorant]

Ah well, yes. By definition, "a thing that exists" cannot not exist.

But that doesn't tell us anything, because we're simply assuming our conclusion by definition. (That's not a criticism of Evie, it's a problem with how this whole question is posed.)...

I think this might be a misunderstanding. By "a thing that exists which cannot not exist", we do not mean a restatement of non-contradiction. We do not mean, "If something exists, then it cannot also simultaneously not exist". Instead, it means, "existence itself has no conditions upon which it is dependent for its existence".