To begin, let's suppose there really is a God.
Or, to sharpen the point a bit more, let suppose there really is a world, a universe - "out there" - existing separately and independently of whatever my own personal experience - thoughts / feelings / beliefs / etc. - of it may be.
Allowing that there may be a reality, a something "out there," that is separate from my experience and beliefs is becoming an increasingly non-functioning concept in our current life. Watch or listen to almost any of the now legion talk shows, and you would be hard pressed to believe that NOTHING is real except what *I* personally think or feel or believe or experience. If *I* think it, then it is real and factual. It is certainly true to my experience.
However, if there really is a reality "out there," separate and independent of my experience of it, then my experience may in fact NOT be an accurate reflection of the thing as it actually is in itself.