The only account that I have been able to devise that subsumes all the different selections of prestigious works made at different times and in different places by different critics is this: Literature is good writing, where by definition ‘good’ yields no fixed definition.
If David subscribes to this account - and it has much to recommend it - he is definitely an existentialist, not an essentialist (as am I) on this question. As for what is literature and what is not, I'm still thinking.
(Politically, though I am often thought to be conservative, I like to think of myself as more of a 19th-century liberal. I am suspicious of concentrated, centralized power. As Lord Acton observed, "The danger is not that a particular class is unfit to govern: every class is unfit to govern." That, of course, could regarded as a conservative sentiment. I definitely do not look to the government - which makes nothing and sells nothing - as the principal means of ameliorating society's discontents. I think of it rather as another - and major - factor contributing to those discontents.)