Would that you were in here, I would show you my wares as proof

[Not that he's trying to trick him or anything. ... He isn't, but he's not going to say anything to make that sound any less suspicious.]

I see. Then you're a western demon. I've never encountered one before.

[Hence the continued conversation and prying, he likes learning. That Crowley has been polite enough and a fine conversationalist just makes it more enjoyable.]

Can you? Are you sure? You're still out there, and I still sit in here alone.