What is Literature?

The latest Booker Prize winner was awarded yesterday. Congratulations to 'The Sense of an Ending' by Julian Barnes. I haven't read it nor any of the others this year so I have no opinion on its quality. From what I understand the author is very well regarded. I also take it that this years shortlist was widely panned.
This has prompted quite a bit of soul searching as to what the Booker Prize should actually be looking for. Here's an intriguing answer from Jeanette Winterson.

There are plenty of entertaining reads that are part of the enjoyment of life. That doesn't make them literature. There is a simple test: "Does this writer's capacity for language expand my capacity to think and to feel?"

As I said, it's intriguing. Under this definition two of my favorite authors, Heinlein and Stephenson, would certainly qualify since they fit that exact quality. Each of them has expanded my 'capacity to think and feel'. I think Stephen King would qualify too.
In fact, the problem here is that I'm not sure this really sets any kind of real limit. Now, if you think that the debate as to whether something is 'literature' or not is meaningless, then so be it. But if you think there should be some meaningful distinction, even one between high and low art, this is the argument that needs to be had.
So back to the definition. I can't think of any of my favorite bits of work that wouldn't qualify. This isn't because I've got such great taste that every thing I like must be of the highest order. It's more that I like things because they 'expand my capacity to think and feel'. Isn't that obvious?