在本文當中，分別從煉丹的目的、方法、設備、藥物及理論預設等角度，深入剖析內外丹的理論特質，最終得出，無論是外丹或內丹，都隱含著一套形上學理論，其所追求的，都是形而上的終極實在。從外丹到內丹的轉變，本質上即是兩種不同形態之形上學的遞擅及較量;如是的轉變，對於形上學的探討，具有重要的啟示。

This article consists of four sections. The first section aims at probing the use of the history of cinnabar in traditional China and the intrinsic meaning of the use of cinnabar. The second section explores the content and nature of external alchemy. We find the most important purpose of external alchemy is to grasp the basic strength of the universe. The metaphysics of external alchemy could be called experimental metaphysics. The third section aims at probing the content and nature of internal alchemy. We also find the most important purpose of internal alchemy is to grasp the basic strength of the universe. The metaphysics of internal alchemy could be called mystical metaphysics. The biggest difference of external alchemy and internal alchemy is method and material. The last section compares the similarities and differences， and advantages and disadvantages， of experimental metaphysics and mystical metaphysics. We think mystical metaphysics is superior to experimental metaphysics. We can obtain important enlightenment from the exploration of the metaphysics of internal alchemy.