Fish don't know they're in water

Fish don't know they're in water.
If you tried to explain it, they'd say, “Water? What's water?”
They're so surrounded by it, that it's impossible to see.
They can't see it until they get outside of it.
This is how I feel about culture.
We're so surrounded by people who think like us, that it's impossible to see that what we think are universal truths are just our local culture.

We can't see it until we get outside of it.