Looking, listening and asking are the four basic diagnostic methods of traditional Chinese medicine, which are collectively called "four diagnoses". According to legend, Bian Que first summed up the invention.

Bian Que's book Difficult Classics, which was written in the Han Dynasty, records: "Knowing by looking is a god, knowing by smelling is sacred, knowing by asking is a work, and knowing by pulse is skillful."

He also explained: "those who watch it will know its disease by seeing its five colors;" Those who smell it, smell its five tones, are not sick; Those who ask and know, ask five flavors to know where the disease is; Those who feel the pulse, examine the mouth, see the deficiency and the excess to know the disease and the viscera. As the saying goes, external knowledge is sacred and internal knowledge is God. "

The diagnostic methods of looking, listening, asking and feeling the pulse play a leading role in traditional Chinese medicine. Xu Chunfu said in the Complete Works of Ancient and Modern Medicine in the Ming Dynasty: "Looking, listening, asking and feeling the pulse are the program of medicine."