This is a summary of a central argument in recent review articles by the
author (cond-mat/0109419, cond-mat/0211005, and cond-mat/0211027). An effective
field theory is derived for the low energy spin singlet excitations in a
paramagnetic Mott insulator with collinear spin correlations.Comment: 12 pages, 4 figures, Proceedings of the International Conference on
Theoretical Physics, Paris, UNESCO, July 200