It is a fundamental tenet of the Course that we are making the world that we see: projection from within causes our perception. This is a particularly difficult concept for “rational” beings to accept, because it requires that we entertain the notion, foreign to ourselves, that we are engaged in mass hallucination with our brothers. Those who have actually seen hallucinations (or visions) will find it easier to accept. Those who have been psychotic have stepped, momentarily, out of the mass hallucination into one seen only by themselves. For these people, the world they normally see will never again seem so real.