Heaven and Hell are choices we make every day
While we are not perfect, our goal must be to live worthy of Heaven by God's Grace.
"Solid Souls" follows the theme of C.S. Lewis' "The Great Divorce" (a response/rebuttal to Blake's "The Marriage of Heaven and Hell"), while not being a re-telling of Lewis' stories ... so read that and Blake on your own. It follows how Lewis represents the "Hell"-bound (the fictional "Gray Town") are visually thinner, more ghostly in appearance, than those who live up on the higher hills (Heaven) ... and appear as more "solid souls").
Rev. Jones carries that to how our everyday decisions can "thin" our souls and make it that much harder to achieve the Heaven on Earth Jesus conscripted us to strive for ... in loving God and loving our neighbor. Great character studies from Arthur's friends and associates, as well as his personal calling, trials, and faith experiences exemplify both results.
Very thought-provoking to how we can repent/reverse/redeem bad choices and insure our arc progresses in the right direction, after our occasional slips in life.