High five for Dr. A but that would include and exclude some things that we do not and do consider life.
Then so be it.
The goal shouldn't be to make a definition that describes something we want to talk about: the goal should be to talk about things in accordance with the way nature "defines" them.
For example, if the definition of "life" fails to exclude viruses, you have to ask yourself why you want to exclude viruses. For another example, if it's impossible to define "dinosaur" such that it excludes birds, you have to ask yourself why you want to exclude birds.
Only if there's a relevant, natural reason to define a specific group of things should we be attempting to define it. We should also acknowledge that "definitions," in the strictest sense, are not part of nature, and so, shouldn't be regarded as binding on nature.
If the definition of life is a spectrum, then we create a problem with the definition of death.
Then so be it.
If that's the reality of it, why would you want the definition to reflect anything else?
Incidentally, I completely disagree with you that a spectrum for “life” makes “death” an ambiguous term. “Death” can only be defined in terms of “life”: so, however you define “life,” “death” is simply the cessation of it. So, “death” always adapts neatly to any definition of “life” that you could possibly care to conceive.
Further, the dichotomy of life and death is not the same as the dichotomy of life and non-life. Rocks and roadkill are two entirely different classes of things in regards to the definition of “life.”
When is a fetus considered alive? This would help us make decisions about the abortion issue.
The use of “alive” in this context is very different from the use of “life” in the context of the biological sciences. The human embryo fits every biological definition of life that I have ever heard, as do the human sperm and egg.
In the context of the abortion debate, the question isn’t about when the fetus fits the definition of “life,” but about when it is sufficiently human to be granted the same rights that humans have. (They made a very similar mistake in the movie Short Circuit, constantly saying that the robot, Number Five, was “alive,” when what they really meant was that Number Five was “self-aware.”)
It is impossible to come up with a single definition of “life” such that abiogenesis, the Bread of Life, anti-abortionism and “Number Five is alive” will all be satisfied.
We need definitions to discuss and make decisions.
I repeat my original statement:
Bluejay, post #16, writes:
Only if there's a relevant, natural reason to define a specific group of things should we be attempting to define it.
There is absolutely no legitimate need for any definition that does not conform to reality, so, definitions must reflect the way things actually are. If the way things actually are is that “life” is only discernible as a spectrum of increasing chemical interconnectedness, then, as I have grown fond of saying,