Gui Zhi Tang or Yu Ping Feng San?

By He Shao-Qi

Someone wrote somewhere that the primary difference between Gui Zhi Tang (Cinnamon Twig Decoction) and Yu Ping Feng San (Jade Windscreen Powder) was that the former is used “when there is a pathogen” while the latter is used “when there is no pathogen”. This mantra is recited over and over, but it seems to me that there’s a problem here.