A fetus is not a being, it is not an organism, it is not an individual. It becomes all of the above when it individuates, that is when it is born. At that moment it becomes independent from its mother, by being able to perform the basic functions needed for the survival of a human being: it gets its oxygen through breathing, it digests food, it starts producing the antibodies required to protect its body in the world in which it will live forever. Until it is born the fetus remains a clump of cells, protected and nourished by the real, existing, fully individuated being: its mother. The fetus does indeed hold the potential to become an individual being. But until it materializes that potential, it is not.
Infancy is not just a new stage of development. An infant is not simply a more developed fetus. As opposed to the difference between an embryo and a fetus, the difference between the fetus and the infant is fundamental not just in an epistemological level, but a metaphysical one. The act of being born is the TRANSFORMATION of the fetus into the infant. The essence of that thing has changed, the thing has become something else, entirely different.
The fetus is indeed human. But "human" used this way is a TYPE of a thing, not the THING itself. A heart, for instance, can be human, reptilian or avian, but that doesn't mean the heart itself IS a man, a crocodile or a chicken. The type of the fetus (or of the heart) does not determine what it IS. It remains a fetus (or a heart). That a heart is reptilian doesn't make it a crocodile. That a fetus is human doesn't make it a human being.
A fetus cannot be killed since it is not a being. A lion, a spider, a sunflower, a bacteria, all of them are living beings and can therefore be killed. A fetus can't, any more than one can kill a pancreas.
A fetus has no rights, since it is not an individual. Only individual human beings have rights. "Human rights" is misleading, giving the illusion that anything human might have rights. Not so. Again, "human" here makes the distinction between the types of BEINGS that have rights, not the types of RIGHTS. It means humans have rights, dogs have not. "Individual rights" would be more appropriate in this context, meaning human beings, such as a pregnant woman, have rights, human hearts (or fetuses) don't.
