This argument is harder to analyze logically, which shows that I should have chosen a more straightforward example. It is invalid, as I originally claimed, if we understand the first premise as saying that every woman has the right to decide only what happens to her body i.e., if a woman has the right to decide on an action, then that action is one that is happening to her body. I think this is a natural way to understand the first premise. However, I agree that the first premise can also easily be read as students in class read it as saying that if a particular action is to happen to a woman s body, then the woman has the right to decide on that action. On this reading, the argument is valid, although anti-abortionists would likely question the first premise so understood.
Abortion is the killing of a fetus.
Therefore abortion is morally permissible. Another example, that s called affirming the consequent . Justification versus explanation. The notion of public-ness, and of public standards of legitimacy or adequacy for moral discussion, is vital if we are to make progress on these issues. We want to have justified beliefs, and we use arguments to justify beliefs that s why the notion of an argument is so important.