For instance, lots of people use the term democracy but often they mean different things by it. For some it refers only to how decisions are made, by letting the numbers count.
Others build in a morally pregnant "was this a good decision" component, so that outcomes they consider too illiberal don't count as democratic.
The same general point applies to debates about multiculturalism. Different people use the term in different ways. In a sense they talk past one another. So for some it's just about being open-minded about other cuisines.
For others, though, multiculturalism as a concept involves a dollop of cultural relativism, of implicitly suggesting that all cultures are pretty much equal and who are we to think ours is better.
Now, often people on each side of such disputes try to win a debate by capturing the word itself, so they get all the rhetorical benefits of being on the side of democracy or of multiculturalism.
I mention this because, in the latter sense of thinking all cultures are more or less equal, I am not a multiculturalist. It is plain to me that the Western tradition and culture in Australia has done more in the past few centuries to advance science (think antibiotics), to advance the status of women, to separate church and state and hence further freedom of speech, and to establish the rule of law than others. Those are plain facts and I see no reason to be embarrassed about saying so.
So I would distinguish between multi-ethnicism and multiculturalism. People who think one race is better than another are plain ignorant, about genetics and a whole lot more.
But people who think some cultures are likelier to produce more learning, more wealth, more happiness than others are saying something wholly different, something factually correct.
That's why British Prime Minister David Cameron says multiculturalism has failed. He says the West needs a "muscular liberalism" that defends our core values.
When certain groups start using multiculturalism as cover for undermining equality before the law and inflating group rights, we all ought to be very cautious. A separate legal regime such as sharia, be it for family law or personal property, is not to be welcomed simply because advocates throw-around terms such as legal pluralism or multiculturalism.
We would need to know in detail its effect on women, on likely integration with the wider society, on children, and a lot more.
And the burden of proof is on those who seek to displace the individualism at the heart of Western culture with something that effectively elevates group rights to a higher plateau.
James Allan is Garrick professor of law at the University of Queensland.
