The following explanation about yin and yang is a summary adapted from H. Wilhelm and R. Wilhelm's book, "Understanding the I Ching: The Wilhelm Lectures on the Book of Change" Princeton University Press 1995 and Fritjof Capra's book, "The Turning Point: Science, Society, and the Rising Culture" Flamingo, Fontana paperbacks 1982 and Martin Palmer's book, "Yin & Yang: Understanding the Chinese Philosophy of Opposites and How to Apply it to Your Everyday Life" Judy Piatkus Publishers.