李杲曰∶药有升、降、浮、沉、化，生、长、收、藏、成，以配四时。春升，夏浮，
秋收，冬藏，土居中化。是以味薄者，升而生；气薄者，降而收；气浓者，浮而长；味浓
者，沉而藏；气味平者，化而成。但言补之以辛、甘、温、热及气味之薄者，即助春夏之
升浮，便是泻秋冬收藏之药也。在人之身，肝心是矣。但言补之以酸、苦、咸、寒及气味
之浓者，即助秋冬之降沉，便是泻春夏生长之药也。在人之身，肺肾是矣。淡味之药，渗
即为升，泄即为降，佐使诸药者也。用药者，循此则生，逆此则死；纵令不死，亦危困矣。
王好古曰∶升而使之降，须知抑也；沉而使之浮，须知载也。辛散也，而行之也横；
甘发也，而行之也上；苦泄也，而行之也下；酸收也，其性缩；咸软也，其性舒，其不同
如此。鼓掌成声，沃火成沸，二物相合，象在其间矣。五味相制，四气相和，其变可轻用
哉。本草不言淡味、凉气，亦缺文也。
味薄者升∶甘平、辛平、辛微温、微苦平之药是也。
气薄者降∶甘寒、甘凉、甘淡寒凉、酸温、酸平、咸平之药是也。
气浓者浮∶甘热、辛热之药是也。
味浓者沉∶苦寒、咸寒之药是也。
气味平者，兼四气四味∶甘平、甘温、甘凉、甘辛平、甘微苦平之药是也。
李时珍曰∶酸咸无升，甘辛无降，寒无浮，热无沉，其性然也。而升者引之以咸寒，则
沉而直达下焦；沉者引之以酒，则浮而上至颠顶。此非窥天地之奥而达造化之权者，不能至
此。
一物之中，有根升、梢降，生升、熟降，是升降在物亦在人也。
李杲说：药物具有升、降、浮、沉、化五种特性，以及生、长、收、藏、成五种变化，用以配合四季的变化。春季对应升，夏季对应浮，秋季对应收，冬季对应藏，土（长夏）居中对应化。因此，气味薄的药物，性质为升而生发；气薄的药物，性质为降而收敛；气浓的药物，性质为浮而生长；味浓的药物，性质为沉而闭藏；气味平和的药物，性质为化而成形。如果说用辛、甘、温、热及气味薄的药物来补益，那就是助长春夏季节的升浮之气，也就是泻除秋冬季节收藏之气的药物。在人体中，这对应于肝和心。如果说用酸、苦、咸、寒及气味浓的药物来补益，那就是助长秋冬季节的降沉之气，也就是泻除春夏季节生长之气的药物。在人体中，这对应于肺和肾。淡味的药物，渗利作用表现为升，泄下作用表现为降，是辅助和引导其他药物的。用药者遵循这一规律就能生存，违背这一规律就会死亡；即使不死，也会处于危险困顿的状态。
王好古说：要使上升的药物转为下降，必须知道使用抑制的方法；要使下沉的药物转为上浮，必须知道使用承载的方法。辛味能发散，其运行方向是横向的；甘味能发散，其运行方向是向上的；苦味能泄降，其运行方向是向下的；酸味能收敛，其药性收缩；咸味能软坚，其药性舒展，它们的不同之处如此之大。拍手能发出声音，浇水能使火沸腾，这两种事物相结合，其中的象数原理就蕴含在其中了。五味相互制约，四气相互调和，其变化岂能轻易使用呢？本草书中不记载淡味和凉气，也是文献的缺失。
气味薄的药物主升：指甘平、辛平、辛微温、微苦平的藥物。
气薄的药物主降：指甘寒、甘凉、甘淡寒凉、酸温、酸平、咸平的藥物。
气浓的药物主浮：指甘热、辛热的藥物。
味浓的药物主沉：指苦寒、咸寒的藥物。
气味平和的药物，兼有四种气和四种味：指甘平、甘温、甘凉、甘辛平、甘微苦平的藥物。
李时珍说：酸味和咸味没有升的特性，甘味和辛味没有降的特性，寒性没有浮的特性，热性没有沉的特性，这是它们的本性决定的。但是，如果用咸寒的药物作为引经药引导升浮的药物，它就会下沉并直达下焦；如果用酒作为引经药引导沉降的药物，它就会上浮并到达头顶。这不是洞察天地奥秘且通达造化权变的人，是不能达到这种境界的。
在一味药物之中，有的根部主升、梢部主降，生的时候主升、熟的时候主降，这说明升降既取决于药物本身的属性，也取决于人的运用。
Li Gao stated: Medicinals possess the properties of ascending (Sheng), descending (Jiang), floating (Fu), sinking (Chen), and transforming (Hua), as well as the changes of generating (Sheng), growing (Zhang), harvesting (Shou), storing (Cang), and completing (Cheng), which correspond to the Four Seasons. Spring corresponds to ascending, Summer to floating, Autumn to harvesting, Winter to storing, and Earth (the central season) to transforming. Therefore, medicinals with thin flavors tend to ascend and generate; medicinals with thin qi tend to descend and harvest; medicinals with dense qi tend to float and grow; medicinals with dense flavors tend to sink and store; medicinals with balanced flavor and qi tend to transform and complete. If one states that tonification is achieved using acrid, sweet, warm, hot, and thin-flavored/qi medicinals, this assists the ascending and floating energies of Spring and Summer, thereby acting as a draining method for the storing energy of Autumn and Winter. In the human body, these correspond to the Liver and Heart. If one states that tonification is achieved using sour, bitter, salty, cold, and dense-flavored/qi medicinals, this assists the descending and sinking energies of Autumn and Winter, thereby acting as a draining method for the growing energy of Spring and Summer. In the human body, these correspond to the Lungs and Kidneys. Medicinals with a bland taste exhibit ascending properties through leaching/diuresis and descending properties through purgation/excretion, serving as assistants and guides to other medicinals. Those who apply medicinals following these principles will thrive; those who oppose them will perish; even if they do not perish, they will be in a precarious and distressed state.
Wang Haogu stated: To make an ascending medicinal descend, one must know how to suppress it; to make a sinking medicinal float, one must know how to carry it. Acrid flavors disperse, and their movement is horizontal; Sweet flavors disperse, and their movement is upward; Bitter flavors drain, and their movement is downward; Sour flavors astringe, and their nature is contracting; Salty flavors soften, and their nature is relaxing. Their differences are thus significant. Clapping hands produces sound; pouring water on fire causes boiling. When these two elements combine, the symbolic principles are inherent within. The Five Flavors mutually restrain each other, and the Four Qi mutually harmonize; how can their variations be used lightly? The Bencao (Materia Medica) omits the mention of bland taste and cool qi, which is also a textual deficiency.
Medicinals with thin flavors ascend: These include medicinals that are sweet-ping, acrid-ping, acrid-slightly-warm, and slightly-bitter-ping.
Medicinals with thin qi descend: These include medicinals that are sweet-cold, sweet-cool, sweet-bland-cold-cool, sour-warm, sour-ping, and salty-ping.
Medicinals with dense qi float: These include medicinals that are sweet-hot and acrid-hot.
Medicinals with dense flavors sink: These include medicinals that are bitter-cold and salty-cold.
Medicinals with balanced flavor and qi, encompassing the Four Qi and Four Flavors: These include medicinals that are sweet-ping, sweet-warm, sweet-cool, sweet-acrid-ping, and sweet-slightly-bitter-ping.
Li Shizhen stated: Sour and salty flavors do not ascend; sweet and acrid flavors do not descend; cold nature does not float; hot nature does not sink. This is their inherent nature. However, if an ascending medicinal is guided by salty-cold substances, it will sink and reach directly to the Lower Jiao (Lower Burner); if a sinking medicinal is guided by wine, it will float and reach the vertex of the head. Only those who have penetrated the mysteries of Heaven and Earth and understood the powers of Creation can achieve this.
Within a single medicinal substance, there are parts that ascend (roots) and parts that descend (tips); raw forms ascend, while cooked forms descend. Thus, ascending and descending depend both on the object itself and on human application.