Unless God is explicit as to the purpose behind what He does, and even sometimes when He is explicit, as believers it is very dangerous to come out with a certain reason *why* God has allowed or willed what has happened to us. This is certainly true with Job - much of what his friends foolishly tell him is precisely such speculation. God flat out tells us "My ways are higher than your ways, My thoughts Higher than your thoughts." However, both as believers and especially as academics, I truly believe it is insightful to ask those questions, even if we can't have them solved absolutely definitively. We just need to know our God and our Bible better than Job's friends :) As to the suffering of Job, these are my own musings, though I believe they have both Biblical foundations and rational coherence, not to mention personal relevance to the average believer.
The text does say that Satan sought to prove Job's weakness before God, and that God did allow Satan to test Job. This testing was thorough, and encompassed virtually every brand of tribulation we can imagine. Why? Why did God need to test Job if a) Job was already righteous and b) God is omniscient and would have known Job would triumph? What value is there in that kind of testing? Why might God have allowed Satan to attack Job again and again at all, even if Job weren't righteous and God weren't omniscient? These are specific questions begging the basic question of why humanity experiences suffering. In order to answer it sufficiently for myself, it is absolutely essential to break out of standard conceptions of intention, cause-effect relationship, and justice.
I do not believe the expression "for the sole purpose of" can *ever* be applied to Yhwh, the God of Abraham, Isaac, and Jacob, the Father of Jesus Christ. He is just too big, too transcendent for that limitation. So what are all, or at least many, of the effects of this testing of Job? First, Job demonstrates where his loyalties really lie. Did God need Job to prove it? No. But what about Satan? Is it of no account when a man or woman of God triumphs by cleaving to the voice of truth in the wake of tragedy and deceit? I think the effects of such a victory go beyond just the impact on Job's life, and actually do effect the Spiritual world in which we struggle. What about Job himself? I think that as a man I need to know precisely of what I am capable. I need to know the man I am at my worst and lowest, because what does it matter how nice or loyal or strong I am when I am well? Is faith, or strength, or any other positive attribute, really that at all if it isn't tested? What is your love towards your fellow man when it is only towards those people who foster affection and return it? Isn't the mark of a loving soul that his/her love knows *no* bounds? That means it stands true in time of trial and tribulation, when the days are tough and the people gruff and anything and everything that can go wrong has. And what about all of Job's friends, both the vocal ones and the ones Scripture does not mention? Have you ever watched a friend lose someone dear, or go through some other equally trying time, and come out on the other side? Have you ever decided you wanted to be more like them, or have more of this remarkable quality you see in them (devotion, strength, persistence, skill etc.) because of the way they have endured? I think that this value cannot be overstated. I also see it going far beyond the circle of Job's closest friends. Consider the many souls destined to read this account since the time of Job? The simple reality is that *everyone* suffers, it is an inescapable quality innate to human-kind; whether you live in a poverty stricken nation bent on civil war and child prostitution, plagued by child-soldiers and HIV AIDS, or whether you are Bill Gates and live in the epitome of luxury - you experience suffering and the longing for better circumstance as well as appreciating the lessening of your burden. Joy and hurt - every man and woman experience them. So what about the many people who have been able to follow Job's example and learn from his friends bad advice? I don't think any of those reasons can be excused from God's "intent." Why did God allow Satan to test Job? Was it so God could provide a positive example in Job? Was it to prove Satan wrong? Was it for Job's sake? Was it for his friends' sakes? Was it for the sake of all of humanity? Was it for the sake of Joshua Ian Smith? My answer would be a resounding "Yes and Amen!" I don't believe *any* of those reasons were less real or "motivating" for God. Job's suffering righted Job's perspective, demonstrated the good and sovereign nature of God, corrected the errant perspective of Job's vocal friends, and provides a model for the rest of us to follow. I would even risk saying that Job suffered as much as any one could, though if worse suffering were possible I would go so far to say that God's will and His justice would still stand. This is to say, even in light of the Holocaust and other unimagineable atrocities wrought and experienced on this Earth, God is still just, still loving, still absolute, and still knows and does what is best.
I could probably say much more, but there is only one other point I find worth emphasizing here. God's "intentions", what He knows and wills a specific circumstance or event to effect, is so infinite and so much beyond our understanding. Any and all of the results of any one thing are in His mind in advance, and are "worked together for good to those who love Him." That is not to say that bad things don't happen - truly "bad" things, things that have no internal inherently redemptive actions - but He can redeem even the worst acts, and integrate them into His ultimate plan of fulfillment. Murder, addictions, lost loves, and all other true injustices - we cannot begin to see *all* of the effects of these things, and we cannot begin to understand the myriad of ways God can use them. To the point, I think God would have killed all of Job's family, all of his livestock, all of his servants, destroyed his livelihood, covered him with a nearly fatal skin disease; ALL of these evils, FOR THE SOLE PURPOSE of showing you how to handle such suffering, if that's what it took. Like I said, I don't think that phrase ever describes our God, but His love for you, His foresight, and His providence *are* THAT ULTIMATE.
The underlying issue, and perhaps the biggest one in Job, is the question of *Theodicy*. Theodicy is just a fancy word for the justice of God. How can God be Just when He allows so much darkness to strike such a righteous man from every side? This is one of the major places where I think we have to suspend our normal mode of thinking. Most people experience this enormous amount of pain, and perhaps rightly ask, "why me?" "What did I do to deserve this?" But really, I think that those questions are completely ridiculous! What did I ever do to merit God's good graces? Have I been so good so as not to deserve those things? Is it even possible for God to give my life more negative baggage than I have positive gifts? It's hard to pin my finger on the best way of wording this question, but what I'm getting it is, aren't we *always* necessarily in God's debt? Don't our blessings and gifts ALWAYS outweigh our curses and so-called "injustice"? Perhaps an analogy is the best way of stressing this point. In relation to other men, we often experience injustice. We are nice to them, they are mean to us - this is unjust. Our sensibility tells us that they owe us something for all of the junk they've tossed at us in response to our goodness. My point is, God constantly, with every breath, is blessing us. He gave us life! And we constantly turn our backs on him, sometimes passively, other times aggressively and quite actively. Is it *ever* even *possible* for us to accrue enough "junk" for God to "owe" us anything? I propose that no, even if our entire family were killed, all that we had ever owned lost, our dearest friends, even our wife, turned against us, and our own bodies stricken to the point of constant unbearable pain, even then, all that God have given us, and continued to give us, would infinitely outweigh the junk. And not just God's past gifts, but his continued presence and goodness in the midst of those hardships. All of the joys, every breath, birth, common graces (sunrises, memories, the experience of color, smell, touch etc.) - any number of things that God sustains in our lives (though admittedly they are hard to see in times of suffering - they are nonetheless there). Just as human experience perceives suffering in the best and worst of situations, so too does it experience joy.
IN BRIEF: I do not believe God's testing of Job can be pinned down to any one reason. I believe there were many, many positive effects of Job's experiences, and that God had them all in mind, even if His loving nature would have allowed Job to suffer for any one of those reasons. I believe that God allowed Job's story to unfold for all of the reasons listed here in so much detail, and quite likely many more beyond my comprehension or realization. I think above and beyond the positive value inherent in this unimaginable tribulation, God also works redemption into and from ALL THINGS and carries His entire creation towards fulfillment (READS: His Kingdom). I believe very strongly in God's Theodicy (Justice) and would assert that no amount of finite injustice could ever outweigh God's infinite blessings, goodness, and providence even in this world, to say nothing of Eternity. We might wish it were otherwise, we might long for less or different kinds of pain, but we never have a right to demand anything from God.** We simply cannot, by our very finitude, ever experience enough "bad" for God to *owe* us some reparation. My friend Andrew Lee asked me about Job, and gave me permission to be wordy. So Mr. Lee, those are my thoughts on Job =)
**It is definitely worth clarifying that my conviction that God is Just and that He knows best does not stop me from getting upset with Him. I experience and respond strongly to pain and suffering. But our perspective and emotions do not change reality. It is the solice I've taken in God's Theodicy that has gotten me through my most difficult times actually. So I know pain is painful, but before you get angry at my seemingly heartless concept of reality, and especially if you're angry with God, consider the broader implications of the nature of God. He is love. He is redemption. He is absolute goodness. Embrace Him like Job...