In order to argue against abortion it is necessary to show that the embryo/foetus has moral status; in other words that it is the type of being which is morally significant and should not be killed unjustifiably.  Human infants after birth are generally accepted to be these types of being.

If we proceed from the assumption that, after birth, human infants are beings with moral status (who therefore enjoy a right to life), the onus is on pro-abortion advocates to show how the nature of a newborn infant is different from the foetus before birth; in other words why birth represents a morally significant dividing line.  It is clear that birth does not change the nature of the being in question in any morally significant way.  To make this event the marker of the infant acquiring moral status is irrational and arbitrary.

One can now ask whether there is any point in pregnancy (or characteristic of the foetus which is developed during pregnancy) which represents a morally significant dividing line, in other words, which changes the nature of the foetus in such a way that it becomes a being with moral status, when it was not such a being previously.  South African law makes no reference at all to the nature of the foetus, but implies that 20 weeks is such a dividing line, as conditions under which abortion is legal are extremely limited after this point.  If 20 weeks is a morally significant dividing line, the onus is on lawmakers to show why this is so.  If one cannot say why his point is morally significant, the decision to disallow abortion after this point, while allowing it before this point, is arbitrary.

Characteristics which have been considered relevant in this regard are quickening, the ability to feel pain, or viability.  However, none of these characteristics can be shown to be morally significant.  The inability to move, feel pain, or survive independently cannot be rationally defended as characteristics which deprive a being of moral status (they do not count as such after birth – imagine the implications if they did).  It is impossible to identify a point in pregnancy which represents a morally significant dividing line, apart from conception, when a new being comes into existence.  Therefore we are logically left with two options – acknowledge that the foetus has moral status from conception, or deny that it has moral status, and accept the implications of this, which is that infanticide is acceptable.  As the second option is morally repugnant to most people, and is not accepted in South African law, we must logically accept that the foetus has moral status from conception.

It would still be possible to defend abortion if one defends the proposition that the mother’s right to bodily autonomy supersedes the foetus’ right to life.  However, if the foetus is a separate being with moral status, who therefore has the right to life, this is a far more fundamental right than the right to bodily autonomy, and this defence therefore does not hold.