The mental factors (caitasika) are the nature and activities of the mind

The operation of the mind consciousness and its mental factors is closely connected with a person's character, temperament, disposition, and wisdom. If you want to understand how the mental factors operate, you can observe each person's facial expressions, gaze, countenance, speech, mannerisms, and the speed of their reactions from the moment they first encounter a matter until they finally make a decision. From this, you can observe the process of each mental factor's operation and its speed, as well as how heavy each person's habitual tendencies are and how good their wisdom is. This whole series of mental activities is both a manifestation of a person's disposition, habitual tendencies, afflictions, and wisdom, and also a manifestation of the mental factors.

Some people are hot-tempered and rather coarse in mind. After encountering people and matters, they only make a rough discernment, paying no attention to right or wrong or to details, and assume that what they have discerned is ultimate and error-free. Then feeling arises—joy, anger, greed, or aversion—with very heavy grasping, and then, without further ado, they make a choice directly. The operation of their mental factors is simple and fast, but the consequences may be unthinkable. Other people, after making a rough discernment and once feeling arises, will again carefully discern and analyze, then reverse their mistaken understanding; their feelings change, and only then do they make a decision. The operation of their mental factors is somewhat more complex and will run repeatedly. Many people, as their discernment deepens continuously, undergo constant changes in the mental factor of feeling; they are swayed by people, matters, and things, their minds completely immersed in them, unable to transcend.

A rational person, if they have not thoroughly understood people, matters, and things, will not develop any thoughts or emotions, nor will they easily make judgments or choices; they do not take their temporary, rough understanding as ultimate, but will observe, discriminate, and deliberate over and over again. A person of cultivation, even when they discern people, matters, and things that they like or dislike, will have a mind unmoved by them—transcendent and liberated.

For careless people, the mental factors operate quickly and simply; for people of meticulous mind, the mental factors operate slowly, deeply, and complexly. For those with heavy afflictions, the mental factors also operate in a complex way, entangled and unclear. Dull people, perhaps after quickly discerning, find their ability insufficient and give up—the mental factors quickly cease; or perhaps they want to discern clearly, and then the mental factors operate extremely slowly: long discernment, long feeling, long deliberation, yet still unable to make a final decision. Clever and wise people may also discern clearly very quickly, deeply understanding its meaning; or they may be able to discern it ultimately in a very deep and detailed way, without error.

The operation of the mental factors is extremely intricate and complex, closely related to each person's character, temperament, disposition, and the weight of their afflictions and attachments, and also closely related to each person's cultivation, spiritual practice, meditative concentration (samādhi), precepts, and wisdom.