Before we start evaluating each of the possible sources of morality, we will need to establish some terms that we will use in the discussion.
First, I mentioned earlier that using “right” and “wrong” when we talk about morality can be confusing, so we’ll use some different words that are specific to moral philosophy. When we talk about actions that are morally bad, instead of saying the action is wrong, we’ll say that it’s impermissible, which just means you shouldn’t do it, or you don’t have permission to do it.
Inversely, if something is morally okay, we’ll call it permissible, which just means that it’s morally okay to do it, or you have permission to do it. This is a good start, but it doesn’t quite cover all the bases. When we say something is “morally the right thing to do”, we might mean that it’s permissible—that it’s okay to do it—but we might also mean something different. We might mean that you should do it—that you’d be morally wrong not to do it. And we need to be able to distinguish between things that are okay to do (permissible) and things that you really ought to do. We’ll call things like that obligatory, which mean that you have an obligation to do it.
So we have three terms to use instead of the vague “right and wrong”:
Permissible – You can do it if you want; it’s morally allowed. (e.g. It is morally permissible to carry your phone in your left pocket, but it would be fine to carry it in your right pocket too.)
Impermissible – You should not do it; it is morally forbidden. (e.g. It is morally impermissible to murder someone.)
Obligatory – You must do it; it is morally required. (e.g. It is morally obligatory to care for your children.)
Someone could disagree with the examples, depending on where they think morality comes from, but you can see how the words are used anyway.
The other moral term we need to establish is one to refer to whomever you think counts morally. That is, whoever should be considered in moral decisions, or in other words, who it would be morally wrong to harm who it would be morally right to benefit. You might care, for example, about things that are not people (that is, things that are not human), like your pets. If you do, it’s probably because you imagine that they are like you in some important way. Perhaps it is that they seem to have character and personality, or perhaps it is simply that they have the ability to feel pleasure and pain. Whatever you think is the source of morality, if it is common to pets as well as humans, then they will count morally.
On the other hand, maybe you don’t think animals can count morally, because they aren’t enough like people. Maybe you believe that they feel pain, but they don’t have rationality, and rationality is where morality comes from. If you think that feeling pleasure and pain is the source of morality, then most animals will count. If you think that rationality is the source of morality, then most animals will probably not count because they don’t have whatever it is that people all have in common.
Because there are different ways to draw the line between what sort of things count morally and what things do not, it is helpful to use the term person, to refer to a thing that counts morally. A person is whatever, according to your worldview, counts morally. It would be morally bad to harm persons, and morally good to benefit them. Depending on where you think morality comes from, there could be persons who are not human (like pets), and there could be humans who are not persons (like corpses). Whichever source of morality you choose will determine what counts as a person. One thing that you will notice is that the term “person” can’t refer to only human beings. This will become clearer as we consider each possible source of morality in detail.