Can't stand to leave it without a search. Here it is--an excerpt and a link:
http://www.geocities.com/neovedanta/a83.html
In the classical allegory of Vedanta philosophy, it is like seeing either rope or the snake. When we see the rope our vision and perception is clear, as if we are in the state of divine consciousness - samadhi. But, as soon as some darkness - ignorance - comes we confuse the rope with snake. Again, someone demonstrates to us by throwing light on the object or by picking it up that what one has mistakenly believed to be the snake is in fact the rope. The important point to note here is that at no point of time the rope ever had turned into a snake; the rope was always the rope. It was our ignorance produced due to clouding of our mind by way of darkness, etc. that caused us to mistakenly see the snake in the rope. The ignorance had superimposed snake over the rope. Much the same way our mind is clouded by ignorance in its present sate and we see superimposition of world - the snake - over Brahman - the rope. Only when a Teacher, a Guru throws light and shows us the true nature of this world can we experience the Brahman therein.
The second point is also of immense importance; and what is that second point? When we see the snake we do not see the rope. We cannot accept that object other than snake. We are afraid of it and run away from it. As in a dream we see a tiger and are terrified by the animal, same way in our dream of illusory snake we are afraid of it. A person dreaming of tiger chasing him gets up all sweating and with palpitating heart, but soon realizes then: 'Oh, what a fool I am; I thought that the tiger was really chasing me!' He thus settles down when he awakens; he understands the truth when his ignorance is destroyed by way of awakening. In case of the snake-rope allegory similar explanation can be applied. When we come out of ignorance, we see the rope as a rope, and all our fears about the snake disappear. While we have given one example of fear to emphasize the point, it is equally and easily understandable that all our attachments to this world are like that dream. Love, fear, jealousy, hatred, passion, anger, infatuation, and so on surface only because of our mistaken belief about the Rope (Reality) as something else.
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C S Shah