Discussion of the first issue, regarding a fetus's right to life, usually draws on the concept of moral personhood. A being is a morally significant person when it is a rights holder, and we are under moral obligation to that being. For example, I am a morally significant person and am entitled to the right to life, which others have a moral duty to acknowledge. The problem for moral theorists is to establish a criterion that explains why I am a morally significant person, and a fly or a worm is not a morally significant person. Some religious philosophers suggest that we are morally significant persons at the moment of conception.
Some philosophers suggest more general criteria such as when a being is self-aware or rational.
These criteria are not exhibited until an infant is one or two years old. The criterion of personhood selected has decisive implications on the morality of abortion. If personhood is confered on a being at the moment of conception, then, all things considered, aborting a fetus is immoral. On the other hand, if we select a criterion such as self-awareness, then, all things considered, aborting a fetus is not immoral. The challenge is in providing reasons in support of one criterion over another.