Although Darwin was able to persuade much of the world that a modern eye could be produced gradually from a much simpler structure, he did not even attempt to explain how the simple light sensitive spot that was his starting point actually worked.

Irreducible complexity is a problem for Darwinian evolution. Whenever we see these complex functional systems we realise that they have to be designed.

In private many scientists admit that science has no explanation for the beginning of life... Darwin never imagined the exquisitely profound complexity that exists even at the most basic levels of life.

Biology has progressed tremendously due to the model that Darwin put forth. But the black boxes Darwin accepted are now being opened, and our view of the world is again being shaken.

In Darwin's time all of biology was a black box: not only the cell, or the eye, or digestion, or immunity, but every biological structure and function because, ultimately, no one could explain how biological processes occurred.

The question is: exactly how did life get here? Was it by natural selection and random mutation or was it by something else? Everybody - even Richard Dawkins - sees design in biology. You see this design when you see co-ordinated parts coming together to perform a function - like in a hand. And so it's the appearance of design that everybody's trying to explain. So that if Darwin's theory doesn't explain it we're left with no other explanation than maybe it really was designed. That's essentially the design argument.

The first point one has to get straight in discussions like this, is that ID is not the opposite of evolution. Rather, it is the opposite of Darwinism, which says life evolved by an utterly unguided, undirected mechanism. If god directed the process of evolution, or rigged the universe to produce complex life, then that is not Darwinism - it is intelligent design.