I don’t see what isn’t clear about it but i will make an attempt to make it clear to you.
The way that I see it, it is like James is saying that the concern of longevity is a vector aiming due North while the concern of joy is a vector aimed due West and then IJOT is a vector aimed at neither of those directions but instead Northwest. So in reality maximizing IjOT does also maximize both longevity and joy at the same time.
He explains in that post (and others) that an attempt to maximize longevity without joy will not work. And he also hints that the attempt to maximize joy without longevity leads to quick death. So the only way to achieve maximum longevity is to make joy a part of the ongoing effort.
He defends his theory in one way and I know that science has demonstrated the truth of it also. Science has shown for a long time that reducing stress (the opposite of joy) increases longevity. And these days they even know precisely why (having to do with cortisone and oxidization, I think)
You stated in our last discussion of this subject that “we all know what joy is … it’s a feeling”. I don’t think that “we all know”. I know that I didn’t and still have questions. James wouldn’t have argued against joy being a feeling but as just demonstrated again in Leyla’s repost of James, he gets down into the ultimate origins and details of things. Superficial names, such as “a feeling”, would never have satisfied James. They just don’t reveal enough truth of the situation (of James’ “MyGod”). James was all about coherency of every detail and in his own words, “leaving no dark corner for the devil to hide” (the “devil” being deception or doubt).
James defined joy as the inner perception of progress whether accurately perceived or not.
And what he is revealing is that by perceiving progress, more true progress is likely. The whole point in perception is to help decide which way to go so it only makes sense that perceiving progress would inspire going in the right direction. No doubt that is a big role in evolution. So longevity is partially dependent upon the joy sensed along the route. If you want to go far, be sure to try to enjoy the trip.
For James, it is clear to me that this whole morality question was very settled and over. And I think he makes a damn good argument (without referencing “God” as the source even once).
I disagree with that but I’m sure that you will stay within your own bubble of belief.