Aquinas Argument Against Abortion

It is indemonstrably true that good is to be sought and its opposite avoided. Here is how we know some things that are fundamentally good.

God is the master of the universe. He gave living beings natural drives and inclinations that allow them to survive and accomplishing their natural ends. These natural ends are naturally good. “Wherefore it has a share of the Eternal Reason, whereby it has a natural inclination to its proper act and end: and this participation of the eternal law in the rational creature is called the natural law.” (S.T.I-II, Q.91 a.2)

Every creature created by God is born with its natural drives and inclinations. Some we share in common with other animals, such as self-preservation, sexual intercourse and taking care of the offspring and others are unique to human beings such as living in society and seeking the truth. If you go against your natural drives and inclinations, you are not being naturally good, especially if you are gifted with reason is fully aware of what you are doing. “Because in man there is first of all an inclination to good in accordance with the nature which he has in common with all substances: inasmuch as every substance seeks the preservation of its own being, according to its nature: and by reason of this inclination, whatever is a means of preserving human life, and of warding off its obstacles, belongs to the natural law.” (S.T.I-II, Q.94 a.2)

In conclusion, God created us with natural ends dictated by the natural laws that we have to follow in order to be good. Preserving life and taking care of the offspring are duties included in these natural laws. Therefore, induced abortion is intrinsically wrong.