How do we know that anything is real? This isn’t a question that usually bothers most people, because we’ve all been brought up to look upon the physical world “out there” as a given. But let’s say that someone actually asks you the question, “How do you know the physical world is real?” What would you answer?
If you pause for a second, there are only two kinds of answers to this question: Either you tell a story or you refer to your own experience. Stories used to be collective myths, generally based on religion, about how God or the gods created the world. But any story, including the most advanced scientific models, depends on belief. If you believe in the Book of Genesis, you will see reality very differently from someone who believes in the Big Bang. To sort out which story is actually true, the second kind of answer arose, defining reality according to our experience. A rock is hard because two people who kick it agree from their experience that it is, in fact, hard.