 professor of biochemistry at Lehigh University, argues that "the fundamental insight of modern biology is that life is based on highly specific complex interactions of molecules." Many cellular systems, he explains, are "irreducibly complex." Many molecules, that is so say, must come together and interact in certain ways before the system can work properly, or indeed at all. The components of a cellular system are intelligible only as parts of a system, and the system does not work unless the components are all in place and functioning in the right way.
The failure of so many modern minds to see the significance of Behe's proposition is the result of a philosophical inheritance with roots in medieval nominalism. It held that the class names (nomina) by which we deal with the world are only names, mental constructs by which we group individual substances for reasons of intellectual convenience. The only real entities are the individual substances, not any common natures that unite them. There is therefore no intellectually discernible natural order in the universe. For a nominalist theologian like William of Ockham, such order as we encounter is dictated by a pure act of God's sovereign will, to which we owe obedience because it is God's will, not because of its inherent intelligibility.
Later generations carried this idea further and reduced the substances themselves to their component elements, either in the laboratory or by mental analysis, then put them together again in the laboratory or in the mind. The parts thus come to be seen as more real than the wholes they form, and the quest for understanding comes to resemble the way in which we understand a machine, by taking it apart and putting it together again. It is not a great step to regarding the several species on the earth as results of accidental changes, which enjoy such stability as they have because of their ability to survive. As Stephen Jay Gould has said, the appearance of each species as it emerges is unpredictable, because the evolutionary process is not going in any predictable direction, but after it happens it is perfectly explainable. Or as journalist George Johnson puts it, "We can reduce downward, but cannot explain upward." The order of the universe is accidental and is intelligible only after the fact.
To return to Michael Behe, Darwinists explain the evolution of an eye that can see by beginning with the chance occurrence of a spot that is sensitive to fight and gradually, by random variation, evolves into a seeing eye. On the contrary, says Behe, "Modern science has shown that the 'simplest' eye-spot requires a cascade of protein molecules -- rhodopsin, transducin, rhodopsin kinase, and more -- which must interact with one another at the level of the cell to produce vision." Furthermore, they must interact in exactly the right proportion and the right way for vision to be possible. Behe concludes that "the interactive complexity of life's machinery fits poorly with a theory of gradual development."
Darwinian evolution is thus a constant process of getting more out of less without an adequate cause. It is not merely that the parts of an eye, and the complex molecules that compose them, are said to evolve by slight random variations, but that they evolve into an organ that did not exist as such before and is capable of performing an action (seeing) that was impossible before. An eye is not a mere sum total of parts in a new conjunction. It is an order of parts so intricately complex that it is questionable whether it is the result of a series of random changes which, by Darwinian definition, were not going anywhere except by sheer accident. Such a process far exceeds the chances of finding a checkerboard of stones on the surface of Mars: The more outruns the capability of the less, because the effect seems to exceed the given Darwinian cause or causes.
There is a further question to be considered: Is complexity all that needs to be explained? Darwinian evolution not only produces more out of less, it brings forth the higher out of the lower. But