“I’ll believe in God if you can prove scientifically that He does things!" How can we respond to such a challenge?
The first thing we must do is disentangle the questions involved here. First, what do we mean by "God's actions"? Second, what do we mean by "science"? And third, can science detect events as God's actions? Let's take them one at a time.
To begin with, we recognize that, after the creation, God works in two ways. First, He maintains the things He created, along with their powers to cause things. Apples keep on tasting good and nourishing us because God keeps maintaining their properties. A soccer goalie deflects the ball because God maintains the properties of the ball, the air, and the goalie's body. Second, God is not limited by the powers of created things. Sometimes He goes beyond their powers if it suits His purpose. We can call the first kind of action the natural (since it works with created natures) and the second the supernatural (since it goes beyond natural powers). Let's be clear about this: Both kinds are God's actions and both serve His purpose.
The sciences study aspects of the world around us in hopes of understanding how they work. Some scientists study the regularities of the world (such as "the angle of incidence equals the angle of reflection"), while others study specific events, trying to reason backward from effect to cause (like Sherlock Holmes, the "scientific detective").
Can God's actions be detected scientifically? It depends on which ones. Because God made His world "very good" (Gn 1:31), it needs no tinkering to keep in operation, so we don't expect that the sciences will "detect" God's natural actions. The reason that an atom's electrons don't crash into the nucleus is not that God holds them apart by a miracle but that He made their properties so that they don't crash.
On the other hand, the sciences may sometimes help us detect a supernatural event because in knowing the properties of natural things, we can tell when these have been transcended. For example, the more we know about how babies come about, the more clearly supernatural becomes the conception of Jesus: There is no natural explanation for it. As C. S. Lewis put it, "No doubt a modern gynecologist knows several things about birth and begetting which St. Joseph did not know. But these things do not concern the main point- that a virgin birth is contrary to the course of nature. And St. Joseph obviously knew that." Advances in medical science have only sharpened the point. We could say the same about Jesus' resurrection: Dead bodies stay dead unless someone with extraordinary power interferes.
This kind of detection works best when it's based on knowledge, not ignorance. It's not just that we don't know how it could happen; rather, we have every reason to believe that it can't happen unless something else is added. The sciences can help us to know better the natures of the things involved and thus to know when "something else" is needed to explain what we see.
Extracted from the Apologetics Study Bible.