Because we assume, unreflectively, that temporal well-being is a necessary constituent of happiness (or even the whole of it) , we also suppose that Job's losses undermine or destroy his happiness. Consequently, we wonder how God could count as good if he allowed these things to happen to a good person such as Job, or we take stories of undeserved suffering to constitute evidence for thinking there is no God. Aquinas, on the other hand, begins with the conviction that neither God's goodness nor his existence are in doubt, either for the characters in the story of Job or for the readers of that story. Therefore, on his view, those who go astray in considering sufferings such as Job's do so because, like Job's comforters, they mistakenly suppose that happiness and unhappiness are functions just of things in this life. And so Aquinas takes the book of Job to be trying to instill in us the conviction that there is another life after this one, that our happiness lies there rather than here, and that we attain to that happiness only through suffering. On Aquinas's view, Job has more suffering than ordinary people not because he is morally worse than ordinary, as the comforters assume, but just because he is better. Because he is a better soldier in the war against his own evil and a better servant of God's, God can give him more to bear here; and when this period of earthly life is over, his glory will also be surpassing.
Eleonore Stump, Aquinas, Routledge (New York: 2003), p. 469.