灵枢经·外揣 Discourse on Inferring the Interior from the Exterior
黄帝曰：余闻九针九篇，余亲受其调，颇得其意。夫九针者，始于一而终于九，然未得其要道也。夫九针者，小之则无内，大之则无外，深不可为下，高不可为盖，恍惚无窍，流溢无极，佘知其合于天道人事四时之变也，然余愿杂之毫毛，浑束为一，可乎？歧伯曰：明乎哉问也，非独针道焉，夫治国亦然。
黄帝曰：余愿闻针道，非国事也。歧伯曰：夫治国者，夫惟道焉，非道，何可小大深浅，杂合而为一乎。
黄帝曰：愿卒闻之。歧伯曰：日与月焉，水与镜焉，鼓与响焉。夫日月之明，不失其影，水镜之察，不失其形，鼓响之应，不后其声，动摇则应和，尽得其情。
黄帝曰：窘乎哉！昭昭之明不可蔽，其不可蔽，不失阴阳也。合而察之，切而验之，见而得之，若清水明镜之不失其形也。五音不彰，五色不明，五藏波荡，若是则内外相袭，若鼓之应桴，响之应声，影之似形。故远者，司外揣内，近者，司内揣外，是谓阴阳之极，天地之盖，请藏之灵兰之室，弗敢使泄也。
Huangdi said: "I have heard the nine chapters on the nine needles; I have personally received their teaching and have grasped much of their meaning. Now, the nine needles begin with one and end with nine, yet I have not yet grasped their essential principle. The nine needles, in their smallness, admit of nothing smaller within; in their greatness, admit of nothing greater without; in their depth, cannot be surpassed from below; in their height, cannot be covered from above. They are vague and indistinct, without any fixed aperture, flowing and overflowing without limit. I know that they accord with the Way of Heaven, the affairs of man, and the transformations of the four seasons. Yet I wish to blend them together down to the finest hair, bundling them all into a single unity — can this be done?" Qibo said: "How penetrating a question this is! It is not the Way of the needle alone that is like this — the governance of a state is likewise so."
Huangdi said: "I wish to hear of the Way of the needle, not of affairs of state." Qibo said: "Now, the governance of a state depends solely upon the Way; without the Way, how could small and great, deep and shallow, all be blended together into a single unity?"
Huangdi said: "I wish to hear this through to the end." Qibo said: "Consider the sun and the moon, water and the mirror, the drum and its echo. The brightness of the sun and moon never fails to cast its reflection; the clarity of water and mirror never fails to capture form; the drum's echo in response never lags behind its sound. When something stirs and moves, the response follows in accord, and the true nature of the thing is thereby fully grasped."
Huangdi said: "How profound this is! A brightness so luminous cannot be obscured; and because it cannot be obscured, it never departs from yin and yang. By combining observation with palpation and verification, one perceives and grasps the truth, just as clear water and a bright mirror never fail to capture form. When the five notes are not manifest and the five colors are not clear, the five viscera are thrown into turbulence — when this is so, the internal and external correspond to one another just as the drum answers the drumstick, as the echo answers the sound, as the shadow resembles the form. Thus, for what is distant, one observes the exterior in order to infer the interior; for what is near, one observes the interior in order to infer the exterior. This is called the utmost expression of yin and yang, the canopy of Heaven and Earth. I ask that this be stored away in the Chamber of the Numinous Orchid, and that it not be allowed to leak out."