When I see people wanting to create "unequivocal definitions", I get nervous. As I imagine myself saying in such real-life exchanges, "Dammit, Jim! I'm an engineer, not a philosopher!" Nor a lawyer. Nor a theologian. Nor any other profession or hobby which plays at redefining reality with definitions.
And I get nervous at such shenanigans because I just know that that philosopher/lawyer/theologian/charlatan is about to pull off a scam.
Now, on the operational level (eg, working engineers and scientists and craftsmen and cooks, etc), we need to define what we are working with based on their actual properties. Furthermore, we need to create definitions that allow us to distinguish between things that are different, especially where that difference makes a difference. But regardless of what names and definitions we give things, reality will tick along exactly the same.
But philosophers/lawyers/theologians/charlatans see definitions differently. They see themselves performing a form of Word Magick in which their new definitions actually change reality. They are ever ready to define reality out of existence.
Biologists are struggling with figuring out what life is. AOK wants to arbitrarily pronounce what is alive. It's like the creationist claims about whether something is a new species. The transition from one species to another takes many generations. Between which two generations do you draw the Line of Demarcation? It's arbitrary. There is even such a thing as a "species problem" in which we try to define whether two populations are of the same or different species. The inability to interbreed is often cited as the criterion for determining that, and yet many closely related species that are definitely different species are still able to interbreed.
I once read some book about sex (over a span of nearly half a century, I cannot be held accountable for being more specific) that sex is not nice and neat, but rather very wet and very messy. Therefore, life itself is infinitely wetter and infinitely messier. How could you possibly tie all that up in a neat little definitional package with a pretty little bow?
One of the founders of the Intelligent Design Movement, Phillip Johnson, is a lawyer. I first encountered him on Nova one night (his book, "Darwin on Trial", was mentioned. It was published in 1991, yet my memory places that episode prior to 1982, so I must assume that my rather vivid memory is faulty here). The argument he was presenting then was that Darwinism violates the rules of evidence for court proceedings. My immediate mental response was, "What an idiot! Science is not a court trial, but rather a police investigation!"
Working scientists create working definitions with which to work. Those working definitions may not be rigorous enough to satisfy arm-chair reality shifters, but they do serve the purposes of the research being conducted.
Ultimately, the problem with any definition is how it can deal with the myriad exceptions. For example, at the local US Marine Corps air station, our Cub Scout pack was given presentations and demonstrations about fire fighting and disaster preparedness. A common part of military fire-fighting training is to present Fire as Living. The trainer lists qualities of life and "shows" that fire displays those qualities of growing and consuming, etc (hey! that was more than two decades ago!). While not binding for biology, it does seem to serve the purpose of instilling a mindset in a firefighter that fire is something that will try to outsmart him.
So then, AOK, just what are you trying to define out of existence through your Word Magick?
Though there was one formulation of that that I particularly liked: "Beating a patch of grass where there once had laid a dead horse." I seem to recall that that had been used in the context of a PRATT.
Do you agree that a population of mules is not a breeding population?
I do believe that that is precisely what NoNukes is saying. Mules are sterile hybrids, therefore by definition they cannot possibly produce any offspring, any new generation of mules. The only way to produce any new generation of mules is to breed horses with donkeys.
Wait a minute. Oh you didn't! Did you just satirize A-Z-dude's whole argument with his insistence on an arbitrary a priori definition? Dude! Subtle!