I think there is a great deal of misunderstanding of the problems with a “God of the gaps” position. This is not a logical fallacy, but rather is more like an observation on the one hand and an implication on the other. I’m not going to try here for a deep philosophical discussion, but rather a simple overview of what I see as the practical application of God of the gaps positively and negatively.
Essentially, “God of the gaps” results when people first credit some observed phenomenon to the action of God, then discover that this phenomenon has a natural explanation, and finally remove that activity from God’s sphere. In reverse it effectively says that God’s action is to be observed in the things that we do not understand.
It is quite possible for someone to hold that God is equally active in both the things we understand and the things that we do not. But that is not the God of the gaps position. When one argues that God is demonstrated by particular things that we do not understand, and that complete understanding would remove that evidence, that person is essentially using a God of the gaps type of argument for the existence of God.
Let’s take an example. In arguing for intelligent design, Michael Behe proposes that there are irreducibly complex systems, that there is no evolutionary explantion (using all natural causes) to explain the existence of such systems. He further claims that there can be no evolutionary explanation because incredibly improbable events would have to occur to produce all the parts of the irreducibly complex system simultaneously and in the proper relationship. The proposed solution is an “intelligent designer” who puts these things together.
Now Behe does not claim that the intelligent designer must be God, but nobody actually proposes any plausibly designer other than God. Any lesser intelligent designer would itself require explanation. So for the moment, let’s assume that the intelligent designer is God, and that Behe’s argument is an argument for the existence of God. There is this system which could not be produced by natural causes, yet it exists, so it must be designed, and through other logic we arrive at God as the designer.
Now suppose I am convinced of the existence of God by this particular argument. Then some fine microbiologist discovers a plausible evolutionary path for producing the system that I was convinced was irreducibly complex. What do I do? Well, if I’m honest I determine that this piece of evidence for the existence of God is no longer valid. If it was the key to my belief, I might have to give up my faith. Otherwise I might still believe, but have one less piece of evidence for that belief. God essentially would have retreated, at least in part, from this section of my universe.
This is not precisely a logical fallacy, although it could lead to one or two. It is quite possible that something of which I am not aware has tinkered with the development of life on earth. Though I personally don’t believe it to be so, God could be intervening regularly in the development of life. One is not required to reject the notion that “God did it” outright.
But of what value is that claim? We have two major problems. First, it’s been done many times. As natural explanations have been discovered, people have seen less and less need to assume God’s activity. Second, God makes a rather lousy hypothesis. Now before my Christian friends accuse me of blasphemy, let me note that my car makes a lousy hypothesis as well, but it’s quite an excellent car. God doesn’t make a good hypothesis because he is not an hypothesis. He is too undefined for that, and more importantly his power is not sufficiently limited in our definition. An hypothesis that explains everything explains nothing. It’s the equivalent of “stuff happens.”
Christian students of the Bible and theology who reject the God of the gaps type of argument do not do so because it is logically impossible. We do so because it conflicts with our understanding of how God functions in the universe, and because as such it has been an untenable position in the past.
Intelligent design resembles a “God of the gaps” argument in that it finds gaps in human knowledge and plugs God into the gap in our knowledge. I cannot be certain that they are wrong in each and every case, though I see no particular reason to believe they are right. But simply asserting that an undefined intelligent designer did it sure sounds to me like the intelligent designer in the gaps.
It’s going to be simple to watch and see. If evolutionary scientists continue to discover new processes and fill in the gaps, then ID will continue to look like a “gaps” type argument and will have all its failings, particular a receding God, and explanations that explain nothing. ID advocates now accuse evolutionary scientists of lacking detailed explanations of the development of various systems, while in turn they simply claim that “the designer did it.” I can’t exclude that as a possibility, but I also can’t see any positive evidence in its favor. It’s pretty clear to me now, and time will serve to make it even clearer.