God does not react. God acts out of the infinity of his being, his every action a manifestation of what has been true from the beginning. This is another way of saying that God is impassible; and if David Bentley Hart is to be believed, it is another way of saying that God is love.
I was thinking about this in relation to redemption, which is often spoken of as a reaction. Specifically, God's reaction to our sin problem. Redemption through and in Christ is therefore God's response to our action. This is how I have always thought of things, and it's why I wasn't quite convinced when Kevin would say something outlandish like "We are redeemed before we are created." I had decent reasons for rejecting that statement, or so I thought, the most forceful being that it seemed to me to make our disobedience necessary to the story of reconciliation. Ivan Karamazov's refusal to accept that the suffering of a little girl could be justified by some greater good was my refusal, and still is. But it is precisely at this point that God being our redeemer before he is our creator shows itself to be good news, for it shows that our evil was not necessary to God being the giver of every good and perfect gift. Creation itself is an expression of the God who redeems, and in the immanent life of the Trinity, we are loved before we are. Indeed we have, all of us, been loved into being, therefore no sin, no suffering has been a necessary evocation of divine love. It was there in the beginning. As Hart says,
God does not have to change or suffer in order to love us or show us mercy -- he loved us when we were not, and by this very "mercy" created us -- and so, as love, he can overcome all suffering.