Without Primary Thinking there would be nothing but chaos - mere phenomena.
It is by God's thinking that the world of creation was formed from chaos - and it is by Man's thinking that he joins God in the work of creation.
Theosis (a.k.a sanctification, divinisation, spiritual progression) is the purpose of Life on earth - our purpose of Men living beyond mere incarnation and death (and of thereby risking the problems of human life, the danger of us rejecting salvation) is so that we may work towards ultimately becoming full deities - sons and daughters of God on the same qualitative level as God.
This entails attaining divine Goodness (which is well known, and tends to be the exclusive focus of most Christians); but also attaining divine Thinking - so that we may each participate in creation.
If we attain divine Goodness without divine thinking we may choose to inhabit and passively experience creation (like a child - indeed as a spiritual child in our nature)...
Or else we may reject this - we may choose 'damnation' which is to live outwith God's creation.
But to be fully mature children of God - we must be able to co-create with God.
In brief: the primary purpose of Man is Love. God wishes deeply to share his creation with divine children, and this is why men and women are created (made literal children of Heavenly Parents).
But then what? Having established a divine family, what do we all do for eternity? It would not be satisfactory for God's children passively to bask-in creation for eternity...
The only coherent answer is that we need to create - which is endless. And to create like God, actively to participate-in God's creation - we must think as God does: Primary Thinking.