confused:
Doesn't this support my point not yours?
I quoted Behe to give you the crux of his argument, in his words, not to support my argument. Behe invented this concept as a supposed problem with evolution, but, as the link I provided points out, there are many problems with his concept. You might want to take a look at the resource.
With regard to the cow example, yes, it's true that a cow can exist without its tail. Now let's think of a scenario in which a cow would not be able to survive effectively without its tail. Let's say that a new population of flies begins taking over the Midwest of the United States. These flies like to eat cow feces, and if possible, they try to get it straight from the source - hot off the press, if you will.
Unfortunately for our bovine friends, these flies carry a powerful poison that kills a large percentage of the cows it affects. Suddenly, the environment favors cows that have strong, nimble tails, since they can effectively fight off the flies. The cows with weak tails die off. After thousands of generations, the tails have adapted to where they are remarkably good at fending off the fly attacks. Take away a cow's tail, and she's as good as dead.
So now what we have is a feature which was not originally "designed" for a purpose, becoming co-opted for that purpose. Then, later, when it became a survival matter, it was honed toward that new purpose. Suddenly, the cow has a feature that it absolutely cannot live without!
To take this a step further, imagine that these cows are so good at defending their rumps that the poisonous flies die off. Now the tails are no longer necessary for survival. Humans come along and discover the tails and wonder why cows are so incredibly good at fending off stupid houseflies. Surely, God must have designed the cow with this marvelous feature as a convenience to the cow. Right?
Obviously, this is just a fictional example, but I think it illustrates how changing needs can create features that a creature "cannot live without." Hope that helps.
SNG