Methods of Argument

There is no agreement on whether and in what sense moral propositions can be 'proved.' Aristotle taught that in each area of inquiry we must seek the kind of knowledge that is appropriate to that area. What exactly might knowledge mean in the case of ethics as opposed to, say, physics or mathematics?

However we define moral knowledge, there are usually ways to argue rationally about the rightness or wrongness (or the goodness or badness) of at least some of our actions. At a minimum, we can use the following techniques:

Sometimes we can show that concepts are incoherent, meaningless, or hopelessly vague. Sometimes we can show that a set of beliefs is internally inconsistent. Sometimes we can show that a belief has morally unacceptable consequences. Sometimes we can show that a belief rests on factual errors.

One very effective way to develop moral arguments is to begin with the cases about which there is agreement and logically deduce a conclusion concerning a disputed case. In the case of abortion there are important points on which many parties agree. For example, most (but not all) agree that infanticide is wrong. This may give you the premise you need to build (or refute) a particular argument.

In order to discover inconsistencies or unacceptable consequences, it is often useful to consider hypothetical cases. These cases may be unlikely to occur in real life, but they can still be revealing. A hypothetical case may reveal that our beliefs have a consequence we had not noticed. As a result, we may decide to change what we believe.