Recently I read a passage from John Duns Scotus's argument for the existence of God in Philosophical Writings, tr. Allen Wolter, O.F.M. (Hackett, 1987) wherein Scotus argues that God as the ultimate efficient cause of everything else is also the ultimate final cause. That is, whereas God brings everything else besides himself into existence, he is also that for the sake of which everything else exists, and after which everything seeks, and in which everything finds its completion and wholeness.
Every per se efficient cause acts for the sake of an end, and a prior cause acts for a prior end; therefore, the first cause acts for the sake of the ultimate end. Now the first efficient cause does not act primarily or ultimately for the sake of anything distinct from itself; hence, it must act for itself as an end; therefore the first efficient cause is the ultimate end. If it were to act per se for the sake of any other end than itself, then something would be more noble than the first efficient cause, for i the end were anything apart from the agent intending the end, it would be more noble than the agent (p. 49).
There is a lot of Scholastic philosophical jargon in this passage, and it is liable to be misunderstood by the average reader without much experience in this domain. For this reason, it may be worth providing a little commentary.
In the first place there is the basic Scholastic assertion that every per se efficient cause acts for the sake of an end. Now an efficient cause is that which causes something to have being, just as the efficient cause of a model car is the person who puts it together. For something to be a per se efficient cause is obviously for it to act as an efficient cause per se, by itself, out of its own nature. To say that every per se efficient cause acts for the sake of an end is not -- I repeat, not -- to affirm that every per se efficient cause acts consciously and intentionally; after all, trees and inanimate substances may still count as per se efficient causes on the Scholastic view of things. The idea is rather that per se efficient causality is intrinsically teleological; the per se efficient cause is intrinsically disposed towards producing the specific effects it does, just as the stomach is intrinsically disposed to digest, a tree to draw nutrients and water from the soil through its roots, etc.
Now by this point in Scotus's extended argument, it has already been proven that God exists as the ultimate efficient cause of everything else. At this point he argues that God is also the end towards which everything strives, the final cause of everything that exists. His argument is that if God acted for the sake of anything else, that other thing would be more noble than God; in some way it would outrank God in value. Now it is important to know that in the Scholastic view of things, being and value are not two separate domains: it is not one thing to be real, another thing to be good, but rather they are somehow simultaneous aspects of the same thing. Since God is the ultimate efficient cause, he exists of himself and brings everything else into existence; in a way, to follow Aquinas, God simply is subsistent existence itself, or ipsum esse subsistens. Consequently God is also the paradigm of all value and goodness. If that is true, there could not be anything more noble than God, anything better than God, some good beyond God which God seeks in creating. Therefore God does not act for the sake of anything else outside of himself, as if he had a need.
This implies, of course, that everything exists for the sake of God. The Bible agrees, too, when it speaks of God, for whom and through whom everything exists (Heb 2.10), and the Father, from whom all things came and for whom we live (1 Cor 8.6). There is at least one important consequence of this: everything finds its fulfillment in God; nothing else can fulfill and perfect a being except that for the sake of which it exists.
This doesn't mean that God is some object to be found somewhere in the world and consumed like food. Rather, I take it that the idea is something like this: true fulfillment comes through an appropriation of God in a way fitting for us given our nature. How do we do this? We become like him through the keeping of his commandments, through the indwelling of the Holy Spirit and the bearing of its fruit (Gal 5.22-3), and by acting in the wisdom of God (Jas 3.17); we pray to him and worship him and thank him for the good things that he gives us; we are trained in love so that we may love others and be unconditionally benevolently disposed towards them, just as he is (cf. Mt 5.43-8); etc. These are the ways to be fulfilled and to enjoy life as God intends it. And if everything exists for the sake of God, these are the things to which God is drawing everything; these are his purposes for everything that exists.