The underlying dogma of "intelligent design" is that life is too complex to have arisen by chance processes.  Proponents of this notion claim to be able to detect a "signal" of design in life, either by recognizing "irreducible complexity" (Michael Behe) or by eliminating all other possibilities, e.g. chance, through an "explanatory filter" (William Dembski).  Both notions focus on the complexity of life, so that is a good starting point for discussion ... and the first major flaw of their arguments.

The only empirical data we have on design is human design (although chimps may be credited with design as well).  And in nature, we can find many examples of the results of chance processes.  In general, designs are simple, nature is complex. Let me give some examples:

A canal is regular, predictable, designed for a purpose.  It was designed to be simple so that it could serve a particular function --  transportation.

A river has no inherent purpose and no design – it is a complex result of the forces of nature. Because of the chance combination of natural forces over the long history, it has evolved complex structures.  Whereas a river is not alive, and therefore can only serve as an analogy here,  it is a natural product that fortuitously serves many functions  (e.g. provides varied habitats for many species, can be used like a canal for transportation).

Light bulbs were designed. They are simple, and every one of each kind is the same.	Fireflies were not designed. Indeed their lighting mechanism is very complex, and every firefly is a little bit different (as would be necessary for evolution).   Although recent advances have been made in understanding the mechanism, tracing the chemical pathways is rather like trying to figure out how each rock got into place in the river.

A battery, although useful to energize many things, is fairly simple.  Every one of each kind is the same, and serves the same designed function.

The mitochondria of a cell, its powerhouse, is quite complex, and the mitochondrial DNA is different from person to person, animal to animal.  How did we get such a complex cell with a separate mitochondria?  From the DNA, it appears that one cell subsumed another into a symbiotic relationship, back when there were nothing but bacteria-like cells on earth. That event led to new possibilities, and we carry the results of it with us today.

Computers are designed, but are more complex than the other examples.  The complexity has in part been due to an evolutionary process of design, building upon innovations not originally meant for computers (e.g. electrical circuits, keyboards), and adding compounding them with more specific designs.  But they are still simple as compared to a human.	Humans are incredibly complex machines with brains that dwarf the complexity of computers.  How can we attribute such complexity to an evolutionary process?  By looking to the fossil record and finding overwhelming evidence for many of the transitions.  By comparing ourselves to other organisms with different brains and different locomotor patterns, and observing commonalities and differences.

Each of the living examples is complex. Intelligent Design proponents throw their hands in the air and say, "look, it’s too complex so it must not have evolved."  But complexity is what we expect from natural systems, and evolutionary biologists are making headway in answering the difficult questions on the origins of every one of these examples.

What then is the importance of Behe's "irreducible" complexity?  That is explored in Part II.