The "God in the gaps" criticism is most often heard in the evolution debate. Naturally so, for what biological IDers complain about, to a large extent, are in fact gaps. Gaps in the fossil record, and knowledge gaps in the explanation of complexity.
I am not a participant in the evolution debate. If I were, I'd spend my efforts on the question of whether there was sufficient time for evolution, not on the gaps in the fossil record.
But, like I said, that's not my fight. I am in the cosmological ID camp. As you are probably aware, cosmological ID theory is based on two observations about our universe: its fine tuning and its uniqueness. Take either support beam away, and the cosmological ID house falls down.
If there is no fine tuning, then there is no evidence for design.
If our universe is not unique, i.e., if we are but one of perhaps an infinite number of parallel universes, then one can logically posit that our particular universe is fine-tuned only because if it were not, we wouldn't be here to talk about it. The multitude of universes, those that are not fine tuned, being sterile, contain no intelligence pondering why they exist in an ordinary, run of the mill cosmos.
Since there is active research in these areas, cosmological ID is falsifiable.
Cosmological ID abhors the gaps.The cosmological ID arguments are not "God in the gaps." Quite the opposite: they are God in the details. Perhaps in biology one can claim that it is our ignorance that unreasonably opens the door to ID, but in cosmology it is our knowledge, not our lack thereof, that points to design. It is not the immaturity of cosmology (and physics) but its achievements that pave the way for ID.
Let me give an example.
Here is an abstract from a recent paper published in Astrobiology:
Anthropic Selection for the Moon's Mass
Dec 2004, Vol. 4, No. 4: 460-468
Dr. Dave Waltham
Department of Geology, Royal Holloway University of London, Egham, Surrey, United Kingdom.
This paper investigates whether anthropic selection explains the unusually large size of our Moon. It is shown that obliquity stability of the Earth is possible across a wide range of different starting conditions for the Earth Moon system. However, the lunar mass and angular momentum from the actual Earth Moon system are remarkable in that they very nearly produce an unstable obliquity. This may be because the particular properties of our Earth Moon system simultaneously allow a stable obliquity and a slow rotation rate. A slow rotation rate may have been anthropically selected because it minimizes the equator pole temperature difference, thus minimizing climatic fluctuations. The great merit of this idea is that it can be tested using extrasolar planet search programs planned for the near future. If correct, such anthropic selection predicts that most extrasolar planetary systems will have significantly larger perturbation frequencies than our own Solar System. Astrobiology 4, 460 468.
To summarize: the earth-moon system is fine tuned to produce, just barely, two great benefits: stability and slow rotation. This gives us predictable, moderate climates and favorable (for life) day-night durations (too fast and the winds/earthquakes etc. would be much more violent, too slow and the day-night and pole-equator temperature differences would be too great.) What the author discovered is the moon is big enough to provide these benefits, as it has to be, but on the other hand if it were just a little bigger an instability would result.
He might also have added that if the moon were bigger the tides would be too violent, causing excessive erosion. And if smaller, they would not be as effective at replenishing the ocean with nutrients.
He might have also added that our present knowledge of planetary formation suggests that it is rare for a small, inner, rocky planet to have a large moon in the first place.1
I have no idea if the author is an IDer. He calls his argument anthropic, which could mean that his view is simply that if it weren't so, we wouldn't be here to talk about it, because the planet wouldn't be habitable. However the scientific prediction he makes, that a planet-moon system like ours is rare, is really a prediction of cosmological ID, in my opinion.
In any case, it is an example of fine tuning. And, more to the point, the fine tuning is known to us not because we don't understand something about the earth-moon system, and rotational stability and drag, and climates, etc., but because we know a great deal about these things. It is not a God in the gaps argument, but a God in the details.
Another "ID" predictionIn a similar (though more spectacular, at least to this nuclear physicist) way, I view Hoyle's anthropic prediction in 1952 of an energy level in Carbon as an ID prediction as well, although Hoyle would never have expressed it that way.
It is interesting to review Hoyle's amazing prediction.
Carbon, essential for life, is formed inside of stars. One way is for three Helium nuclei to fuse:
3He4 → C12
The problem is that it requires three helium nuclei to come together, which is of low probability.
Much more likely is a two step process in which beryllium is formed as a stepping stone.
2He4 → Be8
He4 + Be8 → C12
This requires only two nuclei to interact, and even though it requires it twice, it is far more likely than three nuclei being in the right place at the right time.
This is close to an explanation, but the problem Hoyle faced was that the rate of the reaction He4 + Be8 → C12 was not high enough to explain the abundance of carbon.
At this point Hoyle makes essentially an anthropic argument. We are here, as carbon based intelligent life forms, clearly we wouldn't be pondering this puzzle if we weren't, so somehow the carbon gets produced. What would enhance the rate of formation is a previously unknown excited state of C12 at 7.7 MeV.2
Keep in mind the nature of Hoyle's prediction: it was not via the usual scientific route, which would have been to model the details of the physics of the carbon nucleus and show that our present knowledge of nuclear interactions and many-body dynamics predicts the excited state (virtually impossible in 1952). No, he said, in effect, we are here, so the energy level must be here as well.
Experiments looked for and found the level as Hoyle predicted.
If Hoyle had been an IDer, he could have claimed his prediction as coming from cosmological ID. In a way he did, for (after discovering more anthropic fine tuning in nuclear chemistry) he would famously say: "A superintellect has monkeyed with the physics, as well as the chemistry and biology."3
And so it is for the hundred or so other fine-tuning examples. The more we know, the more the fine-tuning argument is strengthened, not weakened.
God is very much in the details.
1 He might have also pointed out that our moon produces nearly perfect solar eclipses, a rarity for any moon. Although to be fair, this (at the moment) has no known benefit for habitability. It does, however, have a huge scientific benefit.
2 This is essentially because the energy balance of the reaction is simplified. Without that excited state it is hard for the reaction to conserve energy, so it happens less often, and the beryllium is not around for long. As a side "coincidence", the short lifetime of Be8, 10-15 seconds, prevents runaway fusion that would result in early stellar explosions (before life-essential heavy elements are formed), i.e., the instability of Be8 leads to stellar stability. In other words, this represents two fine-tunings: the short lifetime of Be8 for stellar stability, and the fortuitous 7.7 MeV level of C12 that, in spite of the ephemeral nature of Be8, permitted the reaction to proceed at the required rate.
3 Hoyle, Fred, "The Universe: Past and Present Reflections", Ann. Rev. Ast. and Astrophys. 20, 1982, p. 16.