In checking the source of the title I discovered that it is from a book by Tailhard De Chardin, The Future of Man. I wrongly guessed Plotinus who has something of the same sort of pneumatics in his Enneads. In Good Country People O'Connor quotes from Being and Time by Heidegger. She is fond of lay scripture and finds therein ironic themes and inverted doxology.
I note that the Googleamus throws up various glosses on the text called notes. Such explication de texte I never read and on reflection navigating over the reefs of political correctness must be so hazardous for the high school teacher that they would love to leave it out or leave it to the Spark or Monkey interpretations.
There is some shape shifting in this story and exchange of sons. One is reminded of the ancient practice regulated by Brehon law of Tanistry and fosterage. Here of course it is the feeblest of the ancient blood, the liberal son, that inherits. However he is not without an image of Tara's Halls animating his reveries.
Being O'Connor her endings tend to be definite and final, the middle seems to have less of the aggregation of detail of the inveterate fabulist that she was. It was a late story and her illness may have been affecting that energy. As Micheal O Muircearthaigh said about the Clare hurler who went on a severe diet.
You know the ways it is, when you lose a lot of weight, some of your strinth goes with it.