If I find a Clovis point I have no doubt that it is intelligently designed, but if find a chip of flint I can't say for certain that it was or wasn't.
Somewhere in between these two extremes I put the stone fragments I find into one class or the other or a “I can't tell” group.
If I can detect intelligent design in a piece of flint chipped into a Clovis point why cannot the same principles of logic and deduction be applied to that flagellum?
Or does intelligent design only apply to non-living objects?
Clovis points but not cloven hooves, as it were.
Or a pottery shard? True clay pots don't reproduce themselves as far as we know, but we might be able to construct a scenario using known processes whereby they could, however unlikely. What sort of scenario?
A round stone is partially buried in clay. The sun heats the stone more than the clay around it so that a crust of dried clay forms around the stone. A forest fire comes through baking the clay red hot while the stone shatters under the heat. We have our clay pot without invoking intelligence or unique, unobserved processes.
Unlikely, impossible? How do we decide?
“I've given the question some thought, and I don't have an answer. I'm not sure there is one. Maybe every intelligently designed thing is identifiable by its own unique set of characteristics, but there is no set that can identify them all.”
A principle suggested by I.D. is looking at the information embedded in the item under consideration. Taking my Clovis point as an example, it is not the chipping or the material that makes it a tool, there is plenty of chipped flint around, but the relationship of each chipped part to all the others and the overall organization of the various parts into an integrated whole. In short information.
As in the case of my clay pot, we might mentally construct a scenario whereby observed processes could result in a Clovis point but would we seriously accept that as a possibility?
Or would appeal to an intelligent designer provide a better explanation?
To this degree I.D. theories and intelligent design overlap.
Design implies designer? Indeed yes. Which is why the I.D. folk avoid the question since speaking of a designer raises questions about his nature and identity, and not doing that allows one to accept I.D. apart from a particular belief about who the designer is.
One reason that occurs to me is that we have examples of flint chips that aren't Clovis points, so we know what a non-designed chip looks like. As far as I know, we don't have any examples of flagella that don't work right or have parts missing or whatever it would take to decide they weren't designed. We do, as I understand it, have examples of the parts of the flagellum being used for other things, but IDers reject that as evidence that the flagellum could have developed from those parts.
I suppose one could argue that we don't know for sure those non-Clovis chips aren't designed, too. But the identification of Clovis points as designed items isn't just based on what they look like--it's confirmed by finding them in association with other evidence of human habitation and/or with the remains of animals they were presumably used to kill and dress. Someone who wanted to assert those other chips might be designed would have to bring some evidence beyond a simple suggestion.
Unlikely, impossible? How do we decide?
Well, you could try it and see if what you had to do to get that "natural" shard matched any known processes. How much heat will fire clay and also shatter a stone? Does a forest fire generate that kind of heat? Is there any other evidence of a fire? Is the surface of the fired clay smooth or show fingerprints, or is it rough, the way the boundary between dried clay and undried clay might be? Are there lots of examples of this kind of shard around, indicating that it was a common process, or is this the only one, indicating that it might be an accident? Is it found in conjunction with other signs of human activity?