There is much discussion today about the Missio Dei, the mission of God. Many thinkers are predicating 'missional', the attribute of being on mission, to God himself. I recently listened to a series of messages by Mark Young from Dallas Seminary whereby he expounded on the missional nature of God. For the most part I would say God is missional, but I believe this is an attribute of God only in relation to creation and not the Trinity proper.

I am unconvinced in placing missional as an "essential attribute" of God prior to or sans creation. Now, this may take us too far into speculative waters, but here are some first principles I am working from. I consider them uncontroversial in the history of Christian orthodoxy.

The Trinity exists in relational and ontological perfection. God is completely revealed as God, without limit, infinitely among the relationships of Father, Son and Spirit
The universe (or multiverse, or all that is) is not co-eternal with God - so the mission of God cannot be symmetrical for all eternity. Creation is a significant "change"
The universe does not spontaneously emanate from the being of God from eternity - this is related to principle two, but slightly different logically
The Trinity is necessary being, the universe is contingent and was created and continues to exist only by the will of God. Some who hold to a bi-polar view of theism would want to say the mission of God is the same before/after creation due to the universe being necessary "along with" God

Now, from these principles I would argue that God is missional only in relationship to creation, not in and of himself in triune perfection. In my mind the Trinity, from eternity, was not missional. It seems that the missional nature of God results from his decree to create/redeem. So God in himself is not missional, but his love and justice move him on mission "in relationship" to created and fallen beings. I would categorize missional as a description of the action of God according to his decrees. There are other attributes which would be similarly derived. Mercy would be one. God is not merciful in the Trinity, as the Father needs no mercy from the Son, nor the Son from the Father. The Spirit is not need of the mercy of the others, etc. Yet mercy is when the love of God is expressed towards guilty and sinful creatures. One of my friends would call these "contingent attributes" - I prefer "relational attributes" whereby we understand God "in relation to" other beings. This keeps us from "adding attributes" to an unchanging God "after" (logically) creation. So I prefer the term relational attributes, or even relational necessities to describe the relationships between God as God, his created world and designed future. Dr. Bruce Ware uses the term contingent mutability I believe to describe attributes which exist only in relationship to creation. I don't like the word mutability in that construction so I draw these "necessities" as dotted lines between the eternal, perfect, triune God and creation. They exist because of and only in relationship but God himself undergoes no substantial change after creation.

So, now to the "missionality" of the Trinity. Once God decrees a certain world, creates and begins unfolding history, the mission of the Trinity is indeed the glory of God. Now, this mission now exists because there are a certain type of creatures which can in a sense "glorify God" according to what they are. I would argue that dirt, rocks, birds, trees etc have the mission of the glory of God, but of a different species from you and me. Uniquely as the imago dei we have the ability to consciously relate with or rebel against God, rule with him as vice regents, and have the functional capacities (either latent or expressed) to do so. In other words, we are unique beings designed for the mission of the glorifying God. Why is this so? First, our knowledge is in part - we only see dimly. So when God provides "revelation" of himself to us - through either natural or special revelation we "see him" in some way which sin had previously blinded us. As such God is glorified as he self-discloses and we rejoice in Him. Our mission then becomes loving him and "knowing" him in the full sense of relational knowledge. This satisfying relationship propels mission - to further reveal God in our obedience. From this rightly flows a "following of Jesus" to love the poor, serve/steward/rule as redeemed humanity and proclaim the gospel - which is the glory of God revealed in the face of Christ Jesus.

Now, if "glorifying" God at his self-revealing, creature delighting actions (the missio dei) the Trinity, at least in my understanding, does not have this same mission to "glorify" sans creation (remember, I do think God does have this mission post creation). So before (logically) the world, God the Father, Son, and Spirit have full intimate, perfect knowledge that accords with eternal infinite love and harmony. Perhaps we could say the Father reveals himself to the Son and the Spirit for the Father or something of this sort, but this would be odd for beings with "perfect" and complete self-knowledge. Now, once the world and humans are created, by the mysterious will/fiat of God, the showing off or revelation of God is constant. The Father shows off by creating the world through the Son and the Spirit. The Son shows off the Father for all of us in the incarnation, the Spirit shows off Jesus through the church, by regenerating sinners, sending them on missio ecclesia to love the poor, heal the downtrodden, release the yokes, preach the gospel to all creatures. Then in the penultimate glory feast in heaven, we will know fully and explode with eternal, everlasting joy...Oh, what mind has seen what ear has heard what God has prepared...but he has revealed it to us...

Additionally, it seems to me that mission implies activity and activity requiring movement/time. So I believe the Son to be eternally begotten, not made...but not eternally on a temporal mission. At least not the mission we see in Scripture, post creation. If so, then we would have to require the temporal world to be co-eternal with Father/Son - which to me is a big problem.

If the missio dei is about the self-exaltation of God through redemption this seems to imply creation/fall being "in motion" in space-time. As such this may exist eternally in the mind of God, but is not in motion until the decrees formalize at creation. So the very nature of God as self-sufficient, loving, just...seeking to show off his glory to creatures suited to seeing it...seems to sling shot him by necessity (of his own decree/choice) on mission once creation/fall is substantiated. It flows from the trinitarian nature of God, but is not essentially an attribute sans creation. It seems a relational theology is needed - God in relationship to creation IS missional (relational attribute). God in eternal trinitarian existence is perfect, rejoicing in adoration - the mission, if you will, is at perpetual fulfillment and thereby not in motion "in God" - this "fulfilled mission" is then "shared" with creatures through our redemption and eventual glorification when we will become partarkers of this divine nature.

In summary, I would best understand the mission - in terms of space-time relationships within God (post creation, hence space-time) in direct context/relation with all of creation, with a specific role and focus upon "the children of God" - those created imago dei (full sense of imago dei - functional, relational, ontological).

The mission of God therefore might be summarized as follows:

It is decreed by the Father
Who purposes eternally to send Son into the World (space/time) to redeem the whole world from its bondage to decay
Thrust forward through the empowered church by the Spirit...to follow Jesus in the present age: to love the poor, steward/rule the world under God, preach the gospel of the kingdom, accomplished in the substitutionary atoning work of Jesus of an executioner's cross
Resulting in - perpetual mission in this age, until the glorification and temporal fulfillment of the mission of God

Now we have not mentioned the eternal state. In some sense the mission will continue in the Kingdom...it seems it will reach perpetuity and complete fulfillment "in time" - so in a sense Heaven will be a sharing of the pre-creation Trinitarian exaltation, with creatures, in space-time for eternity. So the high happiness of all creation and the perfect self-enjoyment of the Trinity will finally be one...forever.