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On the contrary. No one has ever disputed Irreducible Complexity successfully. What they have shown is that they don't understand the principle of irreducible complexity.

Your case in point. No bacterial flagellum has been found that can operate without the outlined minimum components. It doesn't matter that the parts may be found in other systems. The fact is, the flagellum will not work until all those components are simultaneously re-tasked to the new function.

The key point of IC is that you CANNOT have selection pressures take effect until the ENTIRE unit already exists. Up to that point, it's a purely random process, and any evolutionary biologist will tell you that if you take selection pressure out of the picture, evolution comes crashing down.

Take your case about the flagellum. The components are used in another system. Fine. But, there is NO selection pressure to integrate those components into a flagellum. In fact, there is selection pressure NOT to integrate them, because it puts a resource drain on the organism without a beneficial return. Therefore, in a best case scenario, you have to calculate a RANDOM probability that ALL the needed componentes ALREADY being used in OTHER systems are simultaneously retasked to making a working flagellum, because that is the ONLY scenario that grants a positive selection effect on the organism's survival. Any PARTIAL retasking of components would put an immediate selection pressure AWAY from survival.

And you cannot use the argument of dual use of the components. NO benefit is given the organism until ALL the components are in place. Until then, the dual use is a drain on the organism and will be selected AGAINST.

It's not a hard concept, but it is a frightening one to people who have made evolution their god.

So there's no selection pressure to harvest wood and refine woodworking skills until you are ready to build a violin. Good thinking.

Unfortunately, your description of IC is not the one put forth by the people who invented the term. They did not say you needed a working flagellum in one swoop. What they said was that there was no subset of components that could have a useful function.

But I suspect, and would wager that even your definition is wrong. It will be possible to remove pieces of a flagellum and still have some functionality. In fact I would wager that there are in existence right now, flavors of flagellae having different degrees of functionality. (I'm just guessing about this, but I expect we will here more about it.)

No bacterial flagellum has been found that can operate without the outlined minimum components. It doesn't matter that the parts may be found in other systems.

Ah, but parts of a baterial flagellum can work as something else. No one is suggesting that a flagellum over its evolutionary history was always a flagellum; any more than a wing was always a wing. One could just as easily argue that a wing without properly developed feathers is useless as a wing; but it wasn't useless as a foreleg.

The key point of IC is that you CANNOT have selection pressures take effect until the ENTIRE unit already exists. Up to that point, it's a purely random process, and any evolutionary biologist will tell you that if you take selection pressure out of the picture, evolution comes crashing down.

The entire unit could have come together in crude form from two pre-existing organelles by a single mutation , and then been refined by selective pressure. For example, we know of proton-motive driven enzymes, such as the F₁ATPase, which operate by mechanochemical transduction. If you attach an actin fiber to the head piece of an F1ATPase, you have a primitive flagellum.

Take your case about the flagellum. The components are used in another system. Fine. But, there is NO selection pressure to integrate those components into a flagellum.

Sure there is. In some environments, any motility is a selective advantage. So, you have a mechanochemically coupled enzyme on the cell wall, and you have a secretory system that secretes some sort of polymerizable protein to the extracellular environment. And a mutation causes the secrreted protein to stick to the mechanically coupled enzyme. Presto, you have an external fiber that waggles around, driven by chemical energy. It won't be efficient, but if the bacterium is in a stagnant environment, anything that moves it elsewhere, even randomly, will allow it to supply itself with nutrients faster than diffusion will. And all of a sudden you have something that can evolve, by adding more components, and getting more efficient. And given a billion years and a trillion generations, all of the components will have become so optimized and so interdependent, that someone with very little imagination, or an ax to grind, will come along and say - AHA, IRREDUCIBLY COMPLEX!

My car won't operate without a complex electronic chip that controls its ignition. It is therefore impossible for cars to have evolved without a pre-existing semiconductor industry.