Inspecting and conjecturing the interior and exterior of diseases is a key concept implied in the chapter titled External Conjecture in The Spiritual Pivot ( Líng Shū, 灵枢) .It can be interpreted with a new connotation.In the process of understanding diseases, we can conjecture the nature of diseases by inspecting the external manifestations or the other way around, in this dual direction of inspecting and conjecturing of the interior and exterior, we could have a more comprehensive and accurate knowledge of the disorder.This is a scientific idea of the The Inner Classic ( Nèi Jīng,内经) which matches both the scientific principle and development of TCM theory.This is supplementary to the traditional one direction of conjecturing the interior nature of disease by observing the external manifestations.Therefore a novel idea of inspecting and conjecturing both the interior and exterior could serve as a fundamental principle for TCM diagnosis.