Think about your most deeply-held beliefs. It’s entirely possible that someone who disagrees with you feels just as deeply.
Consider your chronic aches, your devastating pain, your persistent allergy–it’s possible someone else has their own version of this, but different.
And perhaps, your dreams and desires, the ones that keep you up at night, are similar (but different) from the person sitting right next to you.
They’re not making it up. It’s as real as you are.