[Kamog]

So, if everything is an illusion, there is no experiment that you could do to prove it one way or another, because all the results of your experiments would also be an illusion.

As for the universe being a single thought with many Subscribers... it's also possible that there is only ONE Subscriber. I mean, you don't know if anybody else besides you is real. I know that my own thoughts exist but maybe I'm dreaming everything and everybody around me. Sure hope that's not the case - that would be a rather lonely situation to be in.