Does God Exist? (Part 4 of 4)

By Doug Powell

Complexity as design: Irreducible complexity

The irreducible complexity argument states that some things are as simple as they could possibly be and still function. As biochemist Michael Behe puts it, “An irreducibly complex system cannot be produced directly (that is, by continuously improving the initial function, which continues to work by the same mechanism) by slight, successive modifications of a precursor system, because any precursor to an irreducibly complex system that is missing a part is by definition nonfunctional.”

In other words, these things had to be created; they could not have evolved through undirected forces or chance. To illustrate the argument Behe uses the example of a mousetrap. Which part of a mousetrap can be removed and still leave you with a functioning mousetrap?

The answer is that nothing can be removed without completely disabling the mechanism. It did not start out as a piece of wood that caught a couple mice and then mutated to include a spring, which caught a few more mice, which then adapted to include a hammer, which caught even more mice. The mousetrap is made of individual components, which, apart from the whole of the mousetrap, are useless. And if any individual component is subtracted from the whole, then the mechanism is rendered useless. Successive stages of development did not arrive at a mousetrap. The mousetrap could not have possibly evolved. It was first conceived by a mind, then created by an intelligent agent with the power and will to act.

The implications of this are huge. If there are examples of irreducible complexity in biology, then macroevolution — the idea that evolution explains life’s origins and that species evolve from one kind to another — must be false. Behe’s book, Darwin’s Black Box, makes just such a case, using the examples of things like cilium, bacterial flagellum, blood clotting, animal cells, and antibodies, among others. Though these are some of the most basic biological mechanisms we know of, Behe argues that each of these biological machines is irreducibly complex, and that each of the components of the mechanisms is also irreducibly complex and useless apart from the whole.

For example, the bacterial flagellum is the whip-like part of a bacterium that allows it to move — much like an outboard motor — except this motor is water cooled, features a universal joint, has gears for forward and reverse, can reach speeds of 100,000 rpms, and can do self-assembly and repair. It demonstrates an economy of construction and a precision that cannot be accounted for by evolution. The far better explanation is that it was designed and created by an intelligent designer.

Another biological machine often used to illustrate irreducible complexity is the human eye. The eye is made of over 40 different components, each of which contains a number of sub-components. If any one component fails, then vision is impaired. Again, the economy of parts and the precision necessary for vision betrays a designer.

A common objection to the use of the eye as an example of irreducible complexity is that there are a number of different kinds of eyes found in nature and they exhibit a wide variety of complexity. This observation is used to make a case for evolution. But what we see in nature is not a series of steps in an evolutionary chain. Rather, we see a variety of irreducibly complex biological machines.

Just for the sake of argument, let us say the eye did evolve as a result of random processes. What does that give us? An interface with no receiver — like a keyboard that is not attached to a computer. After all, just as there is no actual input without the keyboard being attached to the computer, sight is not sight without a brain to receive it. The eye must connect to the brain somehow. But how does the eye know where the brain is or what a brain is or that it even exists or that it is required to make the eye useful? And how did the eye then wire itself properly to the brain? Why did it not connect itself to the nose or a knee? And even if it did connect to the brain properly (a feat in itself, given all the different parts and functions of the brain), how did the eye know how to speak a language that the brain would understand, and vice versa? Again we need a language created prior to and apart from the existence of the things that will speak the language. And again, an intelligent designer is the best explanation. The eye could not have been self-directed or self-organized.

Tactical note

Understand that the design argument does not prove Christianity alone is true, but the God described by the Bible is consistent with the intelligent designer described by the argument. Christianity, Judaism, and Islam all describe an intelligent designer. Eastern religions have no place for such a being. Most importantly, though, we must remember that the truth of Christianity ultimately does not stand or fall based on the truth of macroevolution. If macroevolution was irrefutably proven to be true tomorrow (in the sense that all species have a common ancestry and could evolve from one kind into new kinds), it would not and could not rule out the possibility of God using it as the agent through which He accomplishes His design. An intelligent agent would still be required to initiate and direct the process, create the languages and codes necessary for the exchange of information, and provide the purpose and design of the biological machines. In short, nothing about human nature will have ultimately changed. We would still be sinners in need of a savior, regardless of how God chose to create us.


The different approaches to the design argument all try to show the same thing: that naturalism can only account for so much; at a certain point its explanatory power fails. But it is not this failure that points to an intelligent designer (the socalled “God of the gaps” theory). The precision of the universe, the nature of information, and the observation that random and undirected forces cannot account for the complexity of living things all lead to a transcendent, personal, intelligent designer.

This post is an excerpt from the Holman QuickSource Guide to Christian Apologetics by Doug Powell. It is used with permission. You can purchase this resource in its entirety here.


Published May 28, 2018