What does this quote from John Steinbeck's East of Eden mean?

Question

“We have only one story. All novels, all poetry, are built on the never-ending contest in ourselves of good and evil. And it occurs to me that evil must constantly respawn, while good, while virtue, is immortal. Vice has always a new fresh young face, while virtue is venerable as nothing else in the world is.”

Answer 1

Adam's answer above is fine until he says that the Steinbeck thinks 'good is unattainable'.

Steinbeck is suggesting that good is always the same but bad is always presenting itself with a fresh face so as to remain alluring and novel.

The battle is to constantly recognise vice and temptation  in its myriad incarnations.

Answer 2

To my mind, he's saying that all our artistic efforts are expressions of the old contest between good and evil, but adds that evil (selfishness) is always regenerating, renewing itself, being applied differently and the ideal of human goodness stays ideal, doesn't change, while everything else changes around it. I think he's suggesting that the ideal of goodness is unattainable.

Thanks, J J :)