I'm actually reminded of the Star Trek TNG ep where they have to have a trial over whether Data is a lifeform.
Admittedly, much of the question is quite philosophical. The original reason for coming up with the question was abortion, but I'm perfectly alright with bringing the question towards other matters. If we can isolate just what separates a human life from nonhuman, and such a thing is created by other humans (cloning, Frankenstein (if Frankenstein's monster fits the criteria), etc.) then such a being would have the rights associated with humanity.
If we accept the premise for the time being that a zygote does not fit the definition of human life, then none of the things which a zygote possesses are considered necessary to the definition of what a human is. I have a number of hypotheses on the matter, but cannot back them up with any specific criteria. DNA was my attempt and was refuted.
If thinking is the criteria, then infants do not fit the criteria and it's acceptable to kill infants. If we argue that babies are capable of growing into being capable of thinking, and expand the definition into something which is capable of growing into being capable of thinking, then zygotes fit that definition.
People who are clinically brain dead are not capable of thinking either, but most would agree that they are still human.
Now, the religious would claim that it's the soul, but science has not proven the existence of the soul, and I'm hoping to find a logical, scientific criteria for human.
I guess I approach this subject the other way around, by which I mean I prefer to focus on the question of whether and under what circumstances we want to accord a thing legal rights, rather than deciding to give a thing legal rights because we've defined it as human.
In Roe v. Wade
, the Supremes' entirely avoided the question of whether a zygote/embryo/fetus has, or should have, legal rights. Instead, the Court limited its focus to balancing the mother's constitutionally protected right to privacy (I prefer to think of the right as one of personal autonomy) against the state's interest in the contents of her womb. The weight of the state's interest in the stuff, according to Roe
, grew during gestation with the improvement of the fetus's chances of surviving outside of mom's body. The closer to extra-utero viability came the fetus, the greater the state's interest in it and the more extensive its right to regulate mom's reproductive choice. Thus, without actually saying so, Roe
permitted each state to decide whether and to what extent to accord a fetus legal rights after viability. One might describe this as allowing the states to accord "personhood" or citizenship or humanity to a fetus at the point of viability.
I suppose the Court's analysis is philosophically unsatisfying, and there can be no doubt it is deeply troubling to the faithful. And, since viability turns in large measure on the state of medical technology, Roe
also placed the balance beam for determining "fetal rights" on a movable fulcrum. Yet, despite its faults, I admire the analysis, not only because it is entirely secular (as I think it must be under the 1st Amendment), but also because it is practical, rather than ideological.
I do not mean to suggest that Roe
provided any meaningful answer to the question of what is "human." However, in limiting its efforts to resolution of the the tension between knowable, competing interests, I think the Court provided a workable template in Roe
for how to treat things which we think are, or might become, like us.