“God forbid,” exclaimed the third hereditary leader of Chabad, known as Zemach Zedek (1789-1866), “that we should say the world is not real!” And yet, nearly every page of classical teaching in the Chabad school insists that the world is “completely nullified” before the great light of God, “like the light of a candle extinguished in the light of the sun.” This is the apparent paradox of materiality which is both real and not real, and it is this dilemma which is addressed through the delicate praxis of contemplative prayer.
http://forums.ssrc.org/ndsp/2013/09/30/to-pray-with-the-tables-and-with-the-chairs/