Moral Relativism: The view that what is morally right or wrong depends on what someone thinks. (To which the claim that opinions vary substantially about right and wrong is usually added.) We can think of this position as coming in two flavours:
(a) Subjectivism: What is morally right or wrong for you depends on what you think is morally right or wrong, i.e., right or wrong is relative to the individual. The 'moral facts' may alter from person to person.
(b) Conventionalism: What is morally right or wrong depends on what the society we are dealing with thinks, i.e., morality depends on the conventions of the society we are concerned with. The 'moral facts' may alter from society to society.
Moral Relativism has become an increasingly popular view in the latter part of this century. Why?
A couple of possible reasons: (i) The Decline of Religion: Religion seems to offer the possibility that morality was independent of us. With a turning away from religion there seems to have come a certain amount of doubt about the possibility of objective morality. As Dostoevsky famously wrote "If God doesn't exist, everything is permissible".
But does it make sense to say that if there's no God, there's no such thing as morality?
Not really. Think back to the Euthyphro problem. What we saw in thinking about it is that it's not as though believing there is a God makes it obvious why some things are right and others are wrong. If we join Euthyphro in saying that God loves the things He does because they are good, then we are saying that things are good (or bad) independently of God (and so, presumably, independently of whether God exists or not).
(ii) Observing Cultural Diversity: Most of us are aware that the world contains many different cultures and that some of those cultures engage in practices very different from our own. Some people, notably the anthropologist Ruth Benedict (1887-1948), have argued that given all this diversity, we should conclude that there is no single objective morality and that morality varies with culture.
Is this a good argument for moral relativism?
Again, not really. First of all, we might dispute whether there is really as much diversity of belief about morality as folks like Benedict say. But even if there is, notice that it is a mistake to conclude based upon differing opinions about morality, that there are no facts about morality.
Imagine this argument being offered approximately 500 years ago: "There is widespread disagreement about the shape of the earth. Some people say it's flat, others say it's spherical, some have even suggested it's a cube. What can we conclude, except that there is really no fact of the matter about what the shape of the earth is?"
The lesson to take from all this is that, while moral relativism might be a correct theory, if it is, it isn't for either of these reasons. You need to do more work than this if you want to be a moral relativist. In particular, you need to confront:
2. Moral Objectivism: The view that what is right or wrong doesn’t depend on what anyone thinks is right or wrong. That is, the view that the 'moral facts' are like 'physical' facts in that what the facts are does not depend on what anyone thinks they are. Objectivist theories tend to come in two sorts:
(i) Duty Based Theories (or Deontological Theories): Theories that claim that what determines whether an act is morally right or wrong is the kind of act it is.
E.g., Immanuel Kant (1724-1804) thought that all acts should be judged according to a rule he called the Categorical Imperative: "Act only according to that maxim [i.e., rule] whereby you can at the same time will that it become a universal law." That is, he thought the only kind of act one should ever commit is one that could be willed to be a universal law.
(ii) Consequentialist Theories (or Teleological Theories): Theories that claim that what determines whether an act is right or wrong are its consequences.
Utilitarianism is the best known sort of Consequentialism. Its best known defender is John Stuart Mill (1806-1873). Essentially, utilitarianism tells us that, in any situation, the right thing to do is whatever is likely to produce the most happiness overall. (The wrong thing to do is anything else.)
Who's right here?
That's clearly a very difficult question to answer.
But here's what we can conclude: it's intellectually lazy (and perhaps false) to say 'morality is all just a matter of opinion'.