To begin with, recall that conventionalism is a relativist theory of ethics that maintains that what is good is determined relative to a society, convention, or culture. On this account, no society or culture is better than another.
A popular way to support conventionalism is to appeal to the cultural differences argument, which goes like this:
This seems like a powerful argument. But the first premise is false. Differences or disagreements across cultures don’t indicate that there can’t be any universal ethical values. We can disagree about things and still have there be a truth to the matter.
Like most ethical theories, the ethical evaluations of conventionalism sometimes make sense to us and sometimes don’t. In other words, conventionalism can provide intuitive and counterintuitive results.
A European in the United States might find some of the conventions counterintuitive. For instance, most people are allowed to own guns in America. The conventionalist will say that this is fine within this culture. This would seem wrong to the visitor.
But if the visitor was a conventionalist, then they would not judge the allowance of gun ownership. This is because a conventionalist thinks that standards of judgment are relative to a culture. On this account you can’t judge one culture by the standards of another.
This stance might seem counterintuitive, though. That’s because we sometimes want to say that someone did something wrong, even if it’s accepted in their culture.
If you’re a conventionalist, then you will say we shouldn’t judge this practice because it’s a culturally relative one. For those that want to stop violence against women, this doesn’t make much sense.