Identifying the Spirit’s causal activity is difficult for many reasons. I want to note two and then show that these problems may actually be opportunities for Christians.
The Mystery Temptation
Before looking at the two problems, I want to address whether we should talk about God as a cause at all. Many theologians want to sidestep causal issues by saying God does not act as an efficient cause.
An efficient cause exerts impact of one entity upon another. Science deals mainly in efficient causes, because it assumes the one thing influences others. We often call this “cause and effect.”
Many theologians are reluctant to think God is one efficient cause among others. They worry that thinking about God in such terms diminishes God to the status they reserve for creaturely causation.
In fact, some say God acts only as a formal or final cause, to use Aristotle’s language. Because science doesn’t deal with final causes (at least explicitly), they believe they can avert tensions between science and religion by saying the two are talking about different kinds of causes.
Some theologians even surmise God influences our present circumstances from a future in which God resides. Wolfhart Pannenberg is one who argues this way. I don’t find such reverse causation plausible, however.
Because of the difficulty of thinking about God as exerting efficient cause, still other theologians appeal to mystery when talking about how the Spirit acts in the world. To this I say, beware of worshipping the God of utter mystery, because you never know who the devil he may be.
In contrast to these theologians, I believe we can talk reasonably about God’s efficient causal influence in the world. Doing so moves the discussion squarely into the realm of science, instead of separating the two like misbehaving children in the backseat.
Talking about God as exerting efficient causation is helpful not only for discussions about the relation between science and theology. It also helps us make better sense of the biblical witness to God’s activity. And affirming God’s efficient causation seems advisable when accounting for the testimonies of those who claim to have experienced God’s activity in either ordinary or extraordinary ways (miracles).
First Problem: We Can’t Perceive Causation
In the first blog of this series, I referred to a biblical passage in which Jesus says God is like the Spirit/wind. Jesus uses the wind analogy to describe how we might have evidence of causation but not know adequately the efficient causes at play. We hear the wind, Jesus says, even though we don’t know precisely its origin or future.
It is true that in experiencing the wind, we may feel its impact on our bodies. And we may see objects swirling around us. This evidence is perceptible with our five senses, and we can plausibly infer the wind is a causal force at play. But we cannot see the causal sequences themselves.
Philosophers of science note that we cannot perceive any causation with our five senses. David Hume famously said we perceive “before” evidence and “after” evidence. But we never directly observe causation itself.
We may feel compelled to infer a causal link between the two events, but we cannot perceive causation directly with sensory perception. Interestingly, Hume’s claim about causation fits what Jesus says about the wind having causal force and yet our senses being incapable of perceiving this causation directly.
Second Problem: We Cannot Perceive God through Senses
The use of wind also fits what Christians have said about God as Spirit. Christians have said we cannot perceive God with our five senses. God is invisible, for instance.
In light of God’s composition, Christians throughout the centuries have sometimes called God “the soul of the universe,” “the holy Ghost,” “a spiritual being,” “the Great Spirit,” etc. “God is spirit,” says Jesus, “and we worship in spirit and truth.”
Although they may say they “taste God,” or “hear God, or “see God,” it is widely acknowledged that these statements are not to be taken literally.
Some Christians have proposed ways to talk about perceiving God’s direct causal activity though other forms of perception beyond our five. For instance, theologian John Wesley argued that at least humans (and perhaps all creatures) have a sixth set of senses: spiritual senses. God as Spirit can directly communicate to creatures that have spiritual sensory apparatus.
Other Christians argue for nonsensory perception of God. This argument says all aspects of the human body and, in fact, all creation can perceive God nonsensorily.
Conclusion
In future blogs, I will be arguing that God acts as an efficient cause (although I also believe God acts through other modes of causation). In these blogs, I will not yield to the temptation to appeal to mystery when it comes to how God acts as a cause in the world.
What I listed as problems for thinking about God as an efficient cause are actually advantages. Here’s why:
While science affirms efficient causation, we cannot actually observe such causation itself. Instead, we must infer such causation occurs based upon what we perceive as the “before” event and the “after” event.
To say God acts as an efficient cause, then, doesn’t require me to point to any particular instance in creation at which we can see God acting as an efficient cause. Remember, we cannot directly percieve 
causation with our five senses. Instead, we must use the same methods of inference for talking about divine efficient causation as we might for nondivine efficient causation.
In addition, Christians believe God is a Spirit imperceptible to our five senses. This means we should not think we can see God out roaming around as a cause. We don’t have to point to an event and say, “Did you see God cause that?” and by this question mean “the causation you observed was God’s.” God is an invisible Spirit, after all.
So… in thinking about the Spirit as an efficient causal force in the world, we’ll not have to strive to prove God can be percieved with our five senses or that God’s causation can be directly observed. And this lowers the bar to a much more manageable level.
And what seem problems are actually advantages!