Among the five aggregate factors of experience (phung-po lnga, Skt. pancaskandha), the aggregate of forms of physical phenomena (gzugs-kyi phung-po) includes:
- Sensory objects (‘dod-yon, desirable sensory objects)
- Physical cognitive sensors (dbang-po, Skt. indriya, sense powers)
- Forms of physical phenomena included (only) among the cognitive stimulators that are (all) phenomena (chos-kyi skye-mched-pa'i gzugs).
Sensory objects are knowable by both sensory and mental cognition. They include:
- Sights (gzugs)
- Sounds (sgra)
- Smells (dri)
- Tastes (ro)
- Tactile and other physical sensations (reg-bya).
Sights include those perceivable to ordinary human eyes and those that are not, such as the bodies of ghosts, gods, hell-creatures, and bardo-beings. In Western terms, they would thus include parts of the light spectrum invisible to human eyes, such as infrared and ultraviolet. Sights also include the revealing forms (rig-byed-kyi gzugs) of constructive and destructive physical actions. The Gelug-Prasangika school also includes here mirages, magicians’ illusions, and the images of distorted vision such as a double moon seen by a cross-eyed person.
In more detail, sights include colors and shapes. The primary colors are blue, yellow, red and white. The branch colors are the colors of clouds, smoke, dust, mist, shadow, sunshine, the sparkle of gems and darkness. Shapes include long, short, flat, curved, high, low, level and not level.
Sounds likewise include those perceivable to ordinary human ears and those that are not, such as high frequency sounds audible to dogs. They include both sounds that communicate information, like speech, and noncommunicating ones, such as the sound of the wind.
Tactile and other physical sensations include four causal ones: solid, liquid, heat and wind (motion); and seven resultant ones: soft, hard, heavy, light, cold, hunger and thirst.
Although the texts are not clear on this point, Sambhogakayas (longs-sku, Corpuses of Full Use) of a Buddha and illusory bodies (sgyu-lus) attained on the complete stage (rdzogs-rim) of anuttarayoga tantra would most likely need to be included as sights. This is because they are visible to the eye consciousness of arya bodhisattvas.
Void-forms (stong-gzugs) attained on the first two stages of the Kalachakra complete stage would also be sights since they are visible to the advanced awareness (mngon-shes, heightened awareness, extrasensory perception) of eye consciousness. This classification is problematic, however. Vasubandhu in A Treasure House of Special Topics of Knowledge (Chos mngon-pa’i mdzod, Skt. Abhidharmakosha) explains that advanced awareness may be with sensory consciousness. Asanga in An Anthology of Special Topics of Knowledge (Chos mngon-pa kun-las btus-pa, Skt. Abhidharmasamuccaya), however, explains that advanced awareness occurs with a mental consciousness that relies on special powers of the eye-sensors (the photosensitive cells of the eyes).
Physical Cognitive Sensors
The physical cognitive sensors are the dominating conditions (bdag-rkyen) for their own specific types of sensory consciousness. They include:
- The photosensitive cells of the eyes (mig-gi dbang-po)
- The sound-sensitive cells of the ears (rna’i dbang-po)
- The smell-sensitive cells of the nose (sna’i dbang-po)
- The taste-sensitive cells of the tongue (lce’i dbang-po)
- The cells of the body that are sensitive to physical sensations (lus-kyi dbang-po).
Forms of Physical Phenomena Included Only among Cognitive Stimulators That Are All Phenomena
Forms of physical phenomena included only among cognitive stimulators that are all phenomena are not knowable by sensory cognition, but are only knowable by mental cognition. Technically, they cannot be included among the five external cognitive stimulators, which refer to the five types of sensory objects, since such forms of physical phenomena can be objects of both sensory and mental consciousness. These special forms of physical phenomena include:
- forms of physical phenomena that make up other things by amassing together (bsdus-pa-las gyur-pa'i gzugs), such as atoms and subatomic particles,
- forms of physical phenomena existing in actual situations (mngon-par skabs yod-pa'i gzugs), such as astronomical distances between stars and microscopic distances between atoms,
- forms of physical phenomena arising from clearly taking them on (yang-dag-par blangs-pa-las byung-ba'i gzugs), such as the subtle nonrevealing forms (rnam-par rig-byed ma-yin-pa’i gzugs) of vows and karmic impulses, as asserted by the Vaibhashika and Gelug-Prasangika schools.
- totally imaginary forms of physical phenomena (kun-brtags-pa'i gzugs), such as sensory objects in dreams and the conceptually implied objects (zhen-yul) of certain conceptual cognitions, such as the bones conceptually implied when imagining the ground filled with bones, but not actually emanating them, or the Avalokiteshvara implied when conceptually visualizing Avalokiteshvara,
- forms of physical phenomena arising from gaining control over the elements (dbang-‘byor-pa'i gzugs), such as the fire or skeletons actually emanated by the power of absorbed concentration (ting-nge-‘dzin, Skt. samadhi).