Our Joy in the Will of GodGod does everything for his glory. It glorifies a thing more to find joy in ascribing value to it than to not. Therefore, God, in making us to glorify him, must have created us to enjoy him, for that glorifies him more than if he created us such that we enjoy some other more than him. Beyond this, and particular to humans, we may choose whether to seek this joy or not, and this makes us moral beings.
Desire for CompanionshipFirst, there is the obvious. If we are created to enjoy ascribing value to God, then we are created for being with God. There is more to our desire for companionship than merely our companionship with God, however, as can be seen throughout scripture where God says "it is not good for the man to be alone" as well as those encouragements to gather together. This is not solely because we are weak by ourselves--God is powerful enough to empower us without working through other people--so there must be some reason behind creating us such that we desire companionship with other humans.
God is trinity, and, as I have said before, his nature is expressed more in something that looks more like him than in something that looks less like him. Thus the Christian community's being one in Christ is a kind of glance at the oneness of God.
Second, God's work for us is interpersonal, and so, for the same reason as he has expressed his attributes in creation to begin with, he desires, and, I would argue, causes it to be the case that his work for us be expressed in our actions toward others, which requires there to be actions toward others. Even if there had been no Fall, and thus no salvific act, this would be good reason for God to say "it is not good for the man to be alone," since God has created the world, and especially humans, made in his image, as an expression of himself, and thus we ought to have some way that we can express the relational attributes of God.
Spirits in Material BodiesThis one gets debated a lot. There is still a lot of back and forth on the issue in christian philosophical journals. On the other hand, the belief that God is an immaterial spirit is not greatly debated. For the same reasons that he must be beyond time, he must be beyond space. Matter is always constrained by space, if it were not it would not be much of matter. If there was some material thing which existed homogeneously everywhere, then it would just as well be immaterial. But who says God is homogenous? He is beyond time, and therefore unchanging. By the same logic, his being beyond space means that he is homogenous.
So God is immaterial spirit. What about us? We are made in the image of God. We show God expresses his spirit-ness by creating spiritual beings, not just angels and such, but in the world, his great tapestry, he has created humans to especially show his nature in the world. Thus, we are spiritual beings.
The FallThe Fall is that event where the first man, Adam, as our representative, chose not to seek his joy in the will of God, and thus sinned. The question, then, is what God did in response to Adam's sin, and, since he represented all of us, what God did in response to our sin in Adam.
As we rejected God, so he allowed his rejection, to a degree. Not, in his mercy, entirely, for to sin is to seek the absence of God, and for God to be entirely absent from us would mean the cessation of our existence. Yet God did withdraw himself from us. God seeks his own joy, and our sin is an affront to him, it flies in the face of his will, so he shows us what it is to be without him, but only a small taste. His love of himself is such that he would not destroy that which he created for his own glory, instead he upholds our essential being. What, then, is the result of this withdrawal of God from us?
Our joy ought to be from God, but he has hidden himself from us. When we are born we do not notice him, though he stands over us, and under us, holding us up. And because we do not see the true object of our joy, we seek other objects of joy, continuing to say that there is no God, as fools, since we only exist because of God's grace. So our wills are all shot through with desire for things that are not worth desiring to such an extent as we desire them, and this is a sinful nature. Now, it is true that we may still choose to seek our joy in God, but our wills are no longer free to do so, they are caught up in so many other desires that are too powerful for it to free itself from. So we live for various things. Good things, but not God, and therefore our living for them is evil.
From this altering of our wills, so that we cannot find the true source of our joy, the right motive for our lives, it follows that we do what is bad for us, we desire some things too much, and others too little. We seek reason at the expense of charity, or renown at the expense of others' lives. We seek to be loved, or to love, but do not know what it is to truly love rightly, for we do not really know what others need, because we do not have it ourselves.
So... because God has withdrawn himself from us, we are wretched. Would that he had withdrawn entirely, that we could not offend him so! But he has not destroyed us, and he has kept us for a reason, he has surely not abandoned us, yet our sin demands that he abandon us. What is the answer to this paradox? Why are we sustained though we sin? How is it that God endures our sinful existence? He must either make us new or display his whole wrath upon us, and if it is only to display his wrath on us, why the wait? In addition to this, I have claimed that one must take the whole scope of what God does before one can necessarily see the wholly good of this world, that it is the best of all possible worlds, though it is full of sinful beings. How can this be?