The nature of illusion is such that the facts of nature lose their importance after passing from their present state. For instance you are not suffering the pain which you may have suffered yesterday or you may not feel the comfort you may have experienced formerly. And if your past condition is of no importance to you just now, the joy or sorrow that you may be experiencing just now will not be with you to-morrow. Such is the case with every moment of life, that which at present seems a reality, when passed becomes a dream and an illusion. This shows that there is nothing within or without which you may call a stable state of existence but in consciousness alone, that is, the consciousness you can recollect you had, the faculty of consciousness when a child, although now childhood may have become a dream to you, and everyday's joy and sorrow in life came and passed.