The basic premise of the article is that there is a reality external to ourselves that can be known outside of our particular systems of language and culture. If there isn't a transcendent "Truth out there" that can be grasped by a particular value system (science, religion, etc) then it is perfectly understandable that two people were convinced they were living in a different world. In other words, all worlds are "fantasy worlds," or if you like, "all worlds are real within the context of their particular systems of language."