According to the abhidharma systems of Vasubandhu and Asanga, phenomena can be divided into those that are tainted (zag-bcas, Skt. sashrava, contaminated) and those that are untainted (zag-med, Skt. anashrava, uncontaminated). In general terms, tainted phenomena constitute what is known as "samsara," the uncontrollably recurring situations of rebirth under the influence of impulses (karma) and disturbing emotions and attitudes, and which entail suffering. Untainted phenomena are either free from these situations or lead to such freedom.
Vasubandhu's Presentation According to the Vaibhashika System
In A Treasure House of Special Topics of Knowledge (Chos mngon-pa'i mdzod, Skt. Abhidharmakosha), Vasubandhu defines tainted phenomena as those that cause tainted phenomena "to increase." In other words, they are those items that cause more tainted phenomena to occur. To understand this definition, we need to know that "tainted" has the general meaning of something that derives from a disturbing emotion or attitude. When such items are the objects cognized by either our own or someone else's limited mind, the result is further disturbing emotions or attitudes on the mental continuum that cognizes them. Also tainted are the five aggregate factors that are in the company of disturbing emotions or attitudes. Thus, Vasubandhu specifies tainted phenomena to be all nonstatic (impermanent) phenomena other than those that constitute the fourth noble truth – that is, excluding all true pathways of mind (true paths, nonconceptual realizations) attained once we have achieved bare, nonconceptual cognition of the four noble truths. True pathways of mind and all static (permanent) phenomena, such as nirvana (liberation, release from all sorrow) and true stoppings (true cessations), are untainted.
Asanga's Presentation According to the Chittamatra System
In An Anthology of Special Topics of Knowledge (Chos mngon-pa kun-las btus-pa, Skt. Abhidharmasamuccaya), Asanga defines tainted phenomena as those that are related to any of the six gateways for being tainted. Thus, Asanga specifies six categories of tainted phenomena:
(1) Phenomena having the identity-nature of being a taint (zag-pa'i bdag-nyid) – the six root disturbing emotions and attitudes and the twenty auxiliary disturbing emotions and attitudes.
(2) Phenomena conjoined with taints (zag-pa-dang 'brel-ba) – the primary consciousness and other mental factors congruent with the root and auxiliary disturbing emotions and attitudes, as well as the cognitive sensors (dbang-po), such as the photosensitive cells of the eyes, that are the dominating conditions (bdag-rkyen) for them to arise.
(3) Phenomena that bind one with taints (zag-pas bcings-pa) – the constructive phenomena that throw one into a future samsaric rebirth.
(4) Phenomena that are the follow-up of taints (zag-pa'i rjes-su 'brel-ba) – the ordinary beings of the plane of ethereal forms (form realm) and plane of formless beings (formless realm), thrown into such rebirth states by the tainted karmic legacies (sa-bon, karmic seeds, karmic tendencies) built up while in the plane of sensory desires (desire realm).
(5) Phenomena harmonious with taints (zag-pa'i rjes-su mthun-pa) – objects which, when focused upon, can cause disturbing emotions or attitudes to arise.
(6) Phenomena that are the outcome of tainted causes (zag-pa'i rgyu-las byung-ba) – the ripened aggregates of a liberated being (arhat), which are the ripened result (rnam-smin-gyi 'bras-bu) of tainted causes, such as craving (sred-pa). This refers to the body, mind, and so on of an arhat during the remainder of the lifetime in which the person has attained liberation. It also refers to the aggregates of any being of lesser attainment than an arhat. When tainted aggregates (zag-bcas-kyi phung-po) are differentiated from obtaining aggregates (nyer-len-gyi phung-po), "tainted" is used with this meaning. Obtaining aggregates are those that include the causes that will obtain for the person further samsaric rebirth, whereas tainted aggregates are those that have ripened from samsaric causes. Thus, the aggregates of the above-mentioned arhats are tainted, but not obtaining ones.
Asanga defines untainted phenomena as those that are not connected with any of the six gateways for being tainted. Thus, untainted phenomena also fall into six categories. Included are true pathway minds, true stoppings, and all static phenomena such as space, and the aggregate factors conjoined with them.
The Gelug Prasangika Presentation
Gelug Prasangika explains tainted phenomena to be those that are mixed with an appearance of true findable existence. Those that are not mixed with such an appearance, such as the aggregates of someone totally absorbed nonconceptually on the voidness of true findable existence, are untainted.