In order to say that some function is understood, every relevant step in the process must be elucidated.

It is often said that science must avoid any conclusions which smack of the supernatural.

The trap does not work until all the parts were there. The system itself doesn't work until you fit all of them together.

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.

Since natural selection requires a function to select, an irreducibly complex biological system, if there is such a thing, would have to arise as an integrated unit for natural selection to have anything to act on.

If you take away a rock from a pile of rocks you haven't changed much. It's still a heap of rocks - just a rock or two smaller. Take away a component from the mousetrap and it isn't a mousetrap any more.

Proteins are the machinery of living tissue that builds the structures and carries out the chemical reactions necessary for life.