Real, like a photograph or a statue.

I think very few of us think of "nothing" even when we're not thinking. It's a matter of suppressing conscious thought--calming the self and focusing on one thing. At times I've found it best just to think "breathe in, breathe out," if that's what it takes.

But that's why I like running as a kind of meditation, too: I get in the zone, so to speak, and I'm not aware of what I'm thinking.