Pluralism

This is one of those words that means a lot of different things, depending on the specific domain. But the general definition – as the word would imply – is “more than one.”

Consider that the Wikipedia page is basically just disambiguation for all the different ways it might be used. You get:

• Political pluralism: the belief that more than one political system can be effective
• Philosophical pluralism: the belief that the world is made up of many things
• Religious pluralism: the belief that many different religious views are valid

I searched for “the opposite of pluralism,” and several resources suggested words like:

• monoism
• homogeniety
• sameness

Also, I noted several definitions of pluralism referring to ethnic divesity, so this might be a common usage of the word. Here’s one, for example:

If you believe in pluralism, you believe that people of all races, classes, religions, and backgrounds should be able to get along on equal footing in society.