What? We all know gui zhi tang as the go to formula for an external attack on tai yang. We also learned in school that it induces sweating which clears the surface of wind. So how can it be a yin tonic Mr Freedman?
Tai yang shang han is tai yang cold damage
Tai yang zhong feng is tai yang wind strike
In a tai yang wind cold attack there are two possibilities, a wind strike or wind cold. Both are an attack of cold but a wind strike is less cold than a wind cold attack.
In a wind strike pattern the circulation of yang wei qi is disrupted by the cold. In a wind cold pattern the cold has closed the surface.
In treating a tai yang wind strike pattern we want to restore the circulation of yang wei qi but also nourish yin to anchor yang. Yin is the mother of yang.
Gui zhi and sheng jiang are both warm and pungent. Gui zhi warms Wood and sheng jiang warms Earth. Together they are 18 grams of yang herbs.
Bai shao is cool sour nourishing of yin and blood. It controls Wood by nourishing Metal. Da zao and zhi gan cao are neutral and sweet. Da zao directly nourishes heart blood and tonifies the Earth. Zhi gan cao nourishes fluids and tonifies function in Earth. Together they are 24 grams of yin herbs.
Since da zao and zhi gan cao both tonify we can consider them yang herbs. Tonifying is restoring funtion and function is yang compared to yin nourishing.
Gui zhi also nourishes yin with its sweet taste so it is partly a yin herb. Bai shao also moves blood so it is partly a yang herb.
Gui zhi tang is a yin tonic that also tonifies yang. Gui zhi tang nourishes deficiency of both yin and yang in a wind strike pattern. Wind is a yang climatic qi that dries yin fluids on the surface of the body. The fluids need to be replaced and gui zhi tang fits that need.