Sometimes, as in dreaming, we seem to be experiencing things very really, yet the reality is only in our heads. We are reminded of the 1966 film by Michelangelo Antonioni called Blow-Up , in which one of the central issues was this same question. A photographer had taken a picture of a murdered man in a park in London and then became uncertain whether this was, in fact, part of reality or an experience of fantasy similar to a drug trip. Within the humanist world view there is no final way of telling. And Antonioni ends his film by making the point graphically.
Tennis players play the game without a ball.
He pauses for a moment, uncertain about what he should do. Here, depicted brilliantly, is the problem of any system which builds its epistemology on man alone. This film was a philosophic statement of the period in which we are living. In 1732 he shocked the world with A Treatise of Human Nature . This had troubled many.