The four diagnostic methods, namely inspection, auscultation and olfaction, inquiry, and pulse-taking and palpation, refer to the four basic procedures used in diagnosing a disease, They are the presuppositions of correct differentiation and effective treatment in TCM.
TCM.四诊即望、闻、问、切，指的是用于诊断疾病的四个基本步骤，它们是中医正确辨证和有效治疗的前提。
When a disease occurs, there must be its abnormal outward manifestations from which the pathological changes may be inferred, as is stated in Danxi's Experience on Medicine （ DanxiXin Fa） , "To want knowing the internal conditions of the body, the external manifestations of the body should be observed ; to diagnose the external parts of the body may also know the internal conditions.
That is because the internal conditions of the body are always reflected on the exterior of the body".The four diagnostic methods examine and learn about the pathological conditions from different angle and aspect and find out the etiology and pathogenesis, thereby providing the basis for TDS. The four methods are related to and supplement one another. They cannot be separated from one another, each having its specific function that cannot be substituted for the others. In clinical practice, only when the four techniques are organically combined can a disease be understood all-sidedly. Thus, a correct diagnosis can be made.
疾病发生时必有相关的病理改变引起的异常外在表现，正如《丹溪心法》所指出的：“欲知其内者，当以观乎外，诊于外者，斯以知其内，盖有诸内者形诸外。”四诊可以从不同角度检查和了解病理状态，找出病因和病机，从而为辨证论治提供基础。四诊相互联系、相互补充，不能相互分离，每一部分都有其特殊的功能，不可代替。在临床实践中，只有将四诊有机联系，才能全面了解疾病，因此，才能做出正确的诊断。
1. Inspection
Inspection is the first diagnostic procedure by which the physician may observe the patient's vitality, complexion, physical build, head,neck, five sense organs, skin, tongue, external genitalia and anus on purpose so as to understand the condition of a disease. TCM holds that the human body is an organic whole. The exterior of the body is closely related to the internal organs. Take observation the vitality and complexion for examples, the vitality refers to the general external manifestations of life activity of the human body, including spirit, consciousness and thinking. And it is the outward sign of the conditions of qi and blood, yin and yang, or the zang-fu organs. The vitality is manifested in manifold aspects, such as eyesight, complexion, facial expressions, physical build, behavior and so on, among which the expression of the eyes is the most important. This is because "all the vital essence from the five zang and six fu organs converges into the eyes." From the observation of vitality the physician may infer the abundance or inadequacy of the vital essence, analyze mildness or the severeness of the disease and predict the prognosis of disease. It is quite evident that the observation of vitality is of an important significance in diagnosing a disease. The manifestations of vitality are as follows; being of vitality, pseudo-vitality, and loss of vitality.
1.望
望诊是诊断的首要程序，通过望诊，医生可以有目的的观察病人的神、色、体质、头、颈、五官、皮肤、舌头、前后二阴，以了解疾病的状况。中医认为人体是一个有机整体，体表和内脏是紧密联系的。以观察神色为例，神指的是人体生命活动的外在表现，包括精神和意识。它是气血、阴阳、脏腑状态的外在征象。神体现于多方面，如眼、面色、表情、体质、行为等，这之中，眼神是最重要的。这是由于“五脏之精上注于目”。通过对神的观察，医生可以了解正气的充足与否，分析疾病的严重程度和预测疾病的预后。很明显察神是诊断疾病的一个重要指征。神有如下表现：得神、假神和失神。