If one wants to debate defining "life" then to be complete one must argue there is no life until the point of death because until then it's an incomplete partial life.
No, one is not really required to do that ... unless they voluntarily constrain themselves solely to the
single definition of the word "life" as you use it in the context above ...
Your premise itself is rather
odd ... since it appears to involve a
misapplication of a definition ...
and I suspect it has been carefully crafted to serve an agenda of some sort ...
Individual words in the English language often have multiple, but somewhat varying, meanings ...
which are often similar or related, but not identical ...
Using your premise above as an example - here are two separate meanings of the word "life" (from some 20+ individual meanings), taken from the link below:
Life - Definition and More from the Free Merriam-Webster Dictionary
Definition:
1a : the quality that distinguishes a vital and functional being from a dead body
5a : the period from birth to death
Clearly, these two things are not the same ... not identical.
You're trying to use a definition more akin to 5a (
leaving aside that they mention "birth" for a second - feel free to substitute "beginning of existence" in lieu of birth instead if you care to), where in reality, definition 1a is more relevant - because the definition we must initially look for necessarily seeks to define the
quality of life itself (as opposed to the quality or qualities that define death), rather the time
period of it.
IOW: defining the
quality of life specifically is of primary importance because that act itself opens the door to discerning the time
period of life ...
Nevertheless, it might be instructive to look at the
change in condition which constitutes the occurrence of death and which results in the ending of the life of a
human being - in order to lend some insight into when the life of a
human being might
start.
In the medical and legal community the permanent and irreversible cessation of brainwave activity and function is considered to be the death of the organism (ie. a human being):
According to the American Medical Association and the American Bar Association, death is legally defined as the "irreversible cessation of all functions of the entire brain, including the brain stem."