A friend also asked me about Theosis. Theosis is that idea that humans on becoming one with Christ are in some sense deified or divinised and so become God themselves.
This is a tricky question and for me it is not so much important to define our relationship with God as to set limits.
The first limit is that we as the created can never cross the line to become god's or God. We are humans, created in God's image, and even in our completely transformed states as eternal beings, will be dependent on God and not God.
On the other hand, the other limit is that cannot simply say that we are human as we are now. We are swept up into Christ at salvation, and the Spirit inhabits us. We are thus drawn up into the Community of the Godhead (perichoresis). The mutual indwelling of Christ, Spirit and us means that we are now in some sense drawn into God. At our transformation we become eternal beings, forever a part of God's being in some sense.
For me, as long as theologians and people are working between these two limits, then it is an exciting doctrine to consider. My major concern is the idea that we speak of divination, theosis, deification in an ontological sense. We are forever created and human. However, I am so excited about what it leads to in my mind to think that I am 'in Christ', and the Spirit is in me, and that I will one day be free from sin and death to experience this fully. At that point, I will sin no more, and the impulse will be consumed. I will then have a creator and all that he has done to live in fellowship with. I will forever be the created and He the creator, I will be the worship and he the worshiped, I will be dependent and he utterly in no need of anything; yet he is mine, and I am his.
Wow! That causes me to pause, well up a bit, and worship... 'My best friend is the creator of the universe' (the Lads).