Apparently the world only exists inside our heads. The way our brains switch what our eyes record from its mirror image, the way in which our senses interpret depending on past experiences, how we hold an idea in our heads of how things should be and we refer to that idea when encountering new experiences.
In much the same way in the political sphere we tend to create the world we want to see irrespective of how it actually is, and believe in our preferred world first. In this way we can hold a political opinion.
Changing perceptions is more than just giving people new ideas, it is helping them give up on old ones.