The following is something of a long selection from Nicholas Cabasilas, The Life in Christ, on why true joy has God alone as its object:
God has emplanted the desire into our souls by which every need should lead to the attainment of that which is good, every thought to the attainment of truth. For these we long in their purity: good rather than evil, truth rather than error; for no one enjoys being deceived or is pleased by going astray and meeting with evil instead of good. Yet no one by desiring them has ever attained them in their purity. What is good and true in our eyes does not correspond to the name, but rather the contrary. Thus it is also clear that neither the power of our love nor the greatness of our joy apparent when the things which we must love and which we enjoy are absent, nor is the compulsion of desire or the ardour of its fire known when the object of desire is absent.
For those who have tasted of the Savior, the Object of desire is present. From the beginning human desire was made to be gauged and measured by the desire for Him, and is a treasury so great, so ample, that it is able to encompass even God. Thus there is no satisfaction, nothing stills the desire, even if men attain to all the excellent things in life, for we still thirst as though we had none of the things for which we long. The thirst of human souls needs, as it were, an infinite water; how then could this limited world suffice?
He, then, is its repose because He alone is goodness and truth and anything else it desires. Those, therefore, who attain to Him are hindered by nothing from loving to the extent that love was implanted into our souls from the beginning, or from rejoicing as much as human nature is able to rejoice, or from anything that virtue and the water of regeneration added to these faculties. Since the good things of ordinary life are not true to their name it is impossible for either desire or joy to be fully effective in them, for even if something seems to be beautiful it is but a paltry spectre of true beauty. But in this case, since , since there is nothing which will stand in the way, love is clearly shown to be wonderous and ineffable and joy to be beyond description. Above all this is so because God has ordained each of these passions with Himself as its object, so that we should love Him and find our joy in Him alone. It follows, I think, that the passion should be in proportion to that infinite goodness and thus, so to speak, be in keeping with it.
In reading that, two thoughts immediately to mind. The first is how much thoughts like this make me prefer soteriology which focuses on participation in God rather than remission of sins. The idea that our souls are made to delight eternally in the infinite goodness of God seems so much richer to me than more aneseptic visions that are preoccupied merely with the expiation of sin.
My second thought returns to the perennial issue of apatheia as an ethical imperative for humanity. The argument here is the reverse from how I typically make it-namely that God is impassible and we ought to be impassible in the way that He is impassible-but it seems nonetheless compelling to me. God has created us with divinely ordained passions which we are to actualize in the ways He has ordained for them (“God has ordained each of these passions with Himself as its object”). Not only are we passionate by design, but our passions are intended to be infinite, coressponding to the object of the passion (“passion should be in proportion to that infinite goodness”). Given that the reality of passions does not remove the necessity of impassibility (apatheia) as an ethical imperative, why would be reject the idea that God can be both passionate (i.e. loving, angry, pleased) and impassible?