Revl,
Good to see you back from "Spring Break," and hope all is well.
I enjoy this question so much; it really pushes the limits of imagination, and hurts the brain a little bit.
Rev asks--
Question: If the natural cosmos is expanding, into what is it expanding?
I think it is expanding into--- whatever is there--or, to look at it another way-- whatever is there after it is expanded into and thus it is recognised as being there by being expanded into.
(Please remember I am not a scientist). (That's obvious eh?)
...and thank you Ellis for a worthy answer. Scientists do no better or worse, I think.
Now that I've passed the dreaded post number, maybe I'll try a comment on this topic. The server only went down for a couple of hours after I hit that repetitive number this time.I figure what is "out there" is the higher dimensions, which inform and direct our spatio-temporal universe.
...String Theories... E-8 Lie Group + 3D + Time = 11 dimensions total... or whatever.
"Out there" is some E-8 unmoved mover;
Preceding and transcending time and space;
Omniscient, omnipotent, and omnipresent;
Filled with unnameable dimensions, beyond comprehension.
What can we call something such as this; the Flying Spaghetti Monster? 
Whatever we call it, it is easy enough to translate into our own terms when we hear it.
Whether you call it "God's Plan" or "The Big Picture of Evolution," they are both inscrutable; but we have faith that the imperative is to continue, to be sustainable.
