Overview of Various Positions taken on the Morality of Abortion 

I. A fetus has a right to life from the moment of conception. 

NOONAN

Noonan argues that, upon conception, a fetus is a human life of equal value to any other human life. 

This makes almost all abortions immoral. The only case in which it is moral is where the mother's life is in danger, and the procedure is a necessary step to save her life. The ONLY thing that permits violation of the fetus' "right to life" is preservation of the mother's life when surgery will kill a developing fetus.

Basically, Noonan is defending the Roman Catholic position that all "procured" or elective abortion is always immoral (read the 1974 Vatican Declaration), BUT the two exceptions outlined by Noonan (ectopic or "tubal" pregnancy and uterine cancer) are regarded NOT as abortions, but as operations in which the death of the fetus is an unintended consequence allowed by the doctrine of double effect.

THOMSON 

For the sake of argument, Thomson simply grants that each fetus has a right to life. 

This makes many abortions immoral, but a right to life does not automatically confer a right to the continued use of the mother’s body.

II. A fetus has a right to life if it is a person 

WARREN 

A fetus does not possess any of the criteria for personhood, so an appeal to its rights cannot prohibit abortion.

This makes all abortions moral.

PROBLEM: But then why is infanticide wrong?

MARQUIS

Once an embryo is established as a distinct individual being and it is developing normally enough that it has a “future like ours,” its right to life should be protected. Its having a future like ours is necessary once it has developed for a short period, and if that development is more or less normal.

This makes almost all abortions immoral.

HARMAN 

Whether a fetus will have a future like ours (including its becoming a person) is contingent. It depends on the actuality of later events (i.e., does that fetus live to become a person?).

This makes all abortions moral.

In this outline, phrases such as “makes it moral” assumes that no other unusual, special circumstances are involved, such as having made a promise.