In brief -
1) The idea of "cocurrence" or "co-operation", part of the
classical doctrine of providence, is that God works with natural
processes to carry out God's actions in the world. In other language,
God is the "first cause" who operates by means of "secondary causes".
It is understand that these secondary causes are God's creations!
This idea in itself certainly doesn't exclude the possibility of
miracles, even if understood as "violations of the laws of nature"
(which I regard as a poor formulation.) Distinction was generally made
between "ordinary"(via such co-operation") and "extraordinary"
(miraculous) providence. But use of this concept DOES make it clear
that we can understand God as being active in everything which happens
in the world without thinking that such action has to be miraculous
intervention of some sort. Thus claims that miracles are needed for God
to "make a difference" are inept.
2) Luther's theology of the cross implies (among other things)
that God works in the world in hidden ways. Thus, tying in with #1, he
speaks of the natural happenings in the world as "masks of God" (_larvae
dei_) "behind which God wishes to remain concealed and do all things."
Even more deeply, the cross means that God is present under the form of
what appears to our reason as the absence of God. Just as on Calvary,
God is "willing to be pushed out of the world" (Bonhoeffer) and to be
considered unnecessary for the explanation of the world. Thus in a real
sense the world can be understood "though God were not given" - even
though God is, in fact, active behind the scenes.
I have set out this theme in a number of places, including
_Journal of the ASA/Perspectives_, under the name term of "chiasmic
cosmology". A summary is in "Chiasmic Cosmology: An Approach to the
Science-Theology Dialogue", _Trinity Seminary Review_ 13.2, 1991, p.83.
3) Van Till's "functional integrity" means just that. God, in
creating the world, operates with such integrity. This is part of the
goodness of creation emphasized in Gen.1. A recent article of his in
_Science & Christian Belief_ deals with the patristic support for this