In his remarkable 1978 essay, "How to Build a Universe That Doesn't Fall Apart Two Days Later," Philip K. Dick discusses the two themes that are most central to his work: "What is reality?" and "What is an authentic human being?"
His speculations and experiences will seem extraordinary to a reader unfamiliar with his work, yet despite what may seem like far-fetched ideas - "somehow the world of the Bible is a literally real but veiled landscape, never changing, hidden from our sight, but available to us by revelation," or the notion that perhaps we all exist in the year 50 A.D. - Dick actually delivers one of the simplest, most elegant and most useful definitions of reality ever formulated:
"Reality is that which, when you stop believing in it, doesn't go away."
Materialist philosophers have expressed similar ideas before (e.g. Straton of Stageira's Talos Principle), but it's particularly interesting to see such a thought expressed by a decidedly more mystical writer, wh#/&$