An Open Universe: How Does God Interact with the World?

The goal of physics is to find a complete description of physical reality - to identify the laws or structure of the physical world that can account for all the phenomena we observe, from galaxy formation to wind patterns to ant colonies. Once the initial conditions of the universe are specified at some early time, the laws of physics completely govern the future evolution of the universe. (There are of course quantum mechanical events in which the state of the universe, or some subsystem of it such as a collection of particles, "collapses" to one among many possibilities in an unpredictable way. But these events are governed by very precise and definite rules of probability.)

What room could this leave for God to interact with the world, or with us? Usually when cosmologists talk about the universe (or perhaps multiverse), they don't consider anything "outside" it that might influence it. That is, it is thought of as a closed system. And indeed, it is hard to imagine how anything outside the universe could affect it in a way that respects the laws of physics, which are very rigid and tightly constrained. In order to answer scientific questions, there's no use to introducing new entities outside the universe unless they can be described with physics and interact with the universe in a way that explains some unexplained phenomenon or observation.

Christianity, however, takes the universe as we know it to be part of a larger reality, which originates with God. God interacts with our world in detailed ways - responding to our prayers, working through specific events in peoples' lives, and most importantly, entering the world in human form in Jesus.

All of these claims seem problematic on the level of physics. For example, how are our prayers accessible to God, and how could God set things up in such a staggeringly precise way that specific events in individual human lives could all be encoded in an earlier state of the universe? We cannot say anything as wishy-washy as "God is all-knowing and all-powerful, so God simply must be able to interact with the world in this detailed way." That is a cop-out, and fails to grasp that it is a scientific question. Although such theological language may carry truth, it is not helpful here, because it forces the issue onto a different playing field, when in fact the playing field of physics is not only legitimate, but essential. We are concerned with God's interaction with a physical world described and constrained by physical laws, which cannot simply be "broken" by God anymore than 1+1 made equal to 3: it is inconsistent with His very nature, and therefore impossible.

We might consider various speculative possibilities. Is the initial state of the universe determined in a very precise way so that the evolution of the universe involves the desired specific events? This might work for a completely deterministic universe, but one might object that it seems ad hoc and inelegant. Is there "room" for God to act through the indeterminate nature of quantum mechanics? It's difficult to see how, without messing with the quantum mechanical rules of probability. But perhaps those probabilities describe the vast array of potential histories of the universe (or actual histories, in the many-worlds interpretation), and the realization of just one of those histories is a separate issue. Perhaps, both in the particular realization of the initial conditions of the universe and the particular realizations of quantum mechanical events, a single history is selected from an infinite number of possible histories. How much "fine-tuning," one might wonder, would this require, in order to sync everything together so that events in human lives work out in a very detailed way?

We cannot say. There is certainly no compelling physical theory of how God may interact with the world, but there is much we do not know of the extent of physical reality, and the origin of our universe. So we would be wise not to hastily rule out the possibility that perhaps the universe is not as closed as it seems.

Whatever the case may be, the sum total of reality - including God, our universe, and perhaps many other realms - is by definition a closed system. And perhaps God's interactions with us should be thought of as in some sense interactions taking place within a physical system, as God too may be physical.