"Isn't what's right just what the majority decides?"
Questions of this kind often reflect students' notions about ethics being relative.
It's important to make it clear to students that though ethical views seem to vary across time and place, ethics is not merely relative.
The view that values are relative to culture is known as cultural relativism. Cultural relativism is a descriptive view - it describes how attitudes about values differ across cultures.
In advocating cultural relativism, students are recognizing the importance of social factors in determining beliefs about how things should be, and are also recognizing how social factors may vary from place to place, and over time. This perspective is useful for respecting the beliefs of cultures that are different from the ones with which we are familiar.
Normative or ethical relativism is a different sort of view, one that holds what is valuable, good or right is determined by society. It is not merely describing variability in beliefs about value, but suggesting how values are to be understood. Often normative relativists suggest that what is ethical is determined by the majority in a society. So, students who think that ethics is just what a majority thinks are normative relativists of this sort.
Though relativism is a common view that students espouse before they reflect on ethical issues, there are all sorts of problems with the view, particularly in our increasingly interconnected world.
Three of the biggest problems with naïve forms of ethical relativism are:
1. Though we are often quite attached to our own social and cultural perspectives, it does not seem to be the case that we are so stuck in our own perspectives that we cannot ever see beyond them.
2. In order for relativism to be true, there would need to be a clear delineation of what or who constitutes a society that determines right and wrong. But this is seldom clear. What counts as one's society/culture? Are societal views always represented by the majority? Need they be?
3. If relativism is true, then minority dissent on ethical grounds is not possible. If we believe that what the majority thinks is right, then we are led to believe that minority opinion is necessarily wrong. For example, consider the effects that such a view of morality would have on the resistance to Hitler, opposition to slavery, or the Civil Rights struggle in this country in the 1960s.
For more discussion of moral relativism go to:
The Stanford Encyclopedia entry on Moral Relativism
For a broad philosophical discussion of relativism go to:
The Stanford Encyclopedia entry on Relativism