We can start with the first point.
Substantiate your claim other than "this is what I believe." Why?
I wrote my views on this point, no need to rehash. My views are based on empirical evidence and inferences we make in everyday life and in life and death decisions of loved ones dealing with severe brain injuries, etc.
How many cells - and organs - does a person need to still be a person?
You wrote, "The majority of us equate "sentience" with being human."
-- If a person is anesthetized for an operation - unconscious and unfeeling - is he no longer a person? Is it because he will become sentient after a while that you consider him an exception? So will the tiniest baby in the womb - in time, those two cells will grow and develop, and become conscious and feeling. In time!
I often wonder if it is possible to ever have a debate without bringing Nazis into it.
To address your point about sentience being lost when we sleep and does that loss of sentience dehumanize you based on my argument. *sigh* This is an interesting train of thought. I would answer that it is a combination of sentience and probability of sentience. When you are sleeping, you have a high probability of waking up sentient, near 100%.
So, by extension doesn't a fetus have a probability of being sentient and shouldn't that probability grant it personhood based on my logic and argument? Not exactly. My conditions for personhood were not "solely" based on sentience, there were other factors as well, namely the ability to theoretically survive on your own outside of the womb was another criteria.
And before the development into what you are sure is a human person, what exactly is it? A nonhuman person? A human nonperson? It certainly will not become a dog or a cat or a rock or a turnip! It is a human being.
I feel one of the mistakes in the abortion argument is the tendency to reduce it to a simple binary yes or no when it is just more complex than that. I consider the fetus a special "quasi case" of undefined humanity.
Technically, the fetus is a parasitic organism. It is incapable of living on its own and needs a host. I know, not a very flattering term for us humans. I consider the fetus the "property" of the mother, again, not a very flattering term. Whatever rights the fetus has are bestowed on it by the mother. If the mother says the fetus is a full fledged human being then I will accept her assessment as superior to my own. Similarly if she decides the other way.
--Is a person in a coma now no longer a human person? Is that how so-called euthanasia is justified? They won't know - Stop the feeling and hydration! They would want to die!
The person is a coma is a human being that is not sentient. Then the question becomes a matter of probability, that is, the probability that this person will become sentient. The Terri Schiavo would be the poster child for this issue but that could be its own thread.
Again, my logic and arguments are based on "real life" decisions and data made everyday. Everyday people pull the plug on brain dead coma patients and it isn't called "murder". Why is that? Why is that acceptable by most people and most societies???
Sperm and Ova instantly begin the process of development. Life is there from that instant beginning. Otherwise, brain and body organs would not be.
*sigh*
Please stop equating life to mean human being. I can spit on the table and it will have life in it. Similarly, it will have human DNA in it as well...
All that 'human beings' determines is species. That of species Homo sapiens. So we don't get to redefine a scientific term to suit our philosophy or relativistic assessment.
If your argument is we are not homo sapiens at conception, then that would be going against established biological fact. Unless you have some alternative science which show we are neither human life nor homo sapiens at conception. DNA is evidence we are and the fact baring a serious defect we have 46 chromosomes.
One would have to be a biology denier to express something already established as settled science.
Please highlight once in my argument where I said a fetus is not homo sapien. I did not. What I have stated is that I don't consider a fetus "fully" human. Similarly, when I said a fetus was not a human being I did so in the full context of SENTIENCE. I acknowledge fully that a fetus has its own unique human DNA. But big deal. Again, I can cut my finger and it will bleed unique human DNA that has life in it. So meh, DNA is not some magic harbinger of personhood. The concept of "personhood" is central to my argument and I don't extend personhood to a group of cells just because it has its own unique human DNA.
My criteria is simple. Brain + internal organs and ability to "theoretically survive on its own" and sentience or rather, a very high probability of attaining sentience (since I guess we don't attain self awareness until we are around 2 years old).
You can try to lawyer my argument finding little loopholes to belay logical inconsistencies but it will be near impossible becuase my arguments are based on the empirical of everyday life.
How many of us have organ donor checkmarks on our Driver's licenses right now? How many people pull the plug on loved ones whom machines could easily keep alive longer? how many couples get pregnant but don't tell anyone until 3 or 4 months just so they can "be sure" the fetus is really viable and won't miscarry?
GIven that up to 20% of pregnancies are miscarriages, how many of us have been to funerals of 2 week and 3 week old fetuses that were miscarriages???...
If actions were equivalent to words then things would be different. People would name their fetuses instead of waiting for actual birth to declare a name. People would hold funerals for miscarriages even if it were a week old. Sorry, the data and the actions the vast majority of us take in this regard don't match your theoretical constructs.