➥ āyatana: 1. 'spheres', is a name for the four immaterial absorptions; see jhāna (5-8). 2. The 12 'bases' or 'sources' on which depend the mental processes, consist of five physical sense-organs and consciousness, being the six personal (ajjhattika) bases; and the six objects, the so-called external (bāhira) bases - namely:

• eye, or visual organ visible object
• ear, or auditory organ sound, or audible object
• nose, or olfactory organ odour, or olfactive object
• tongue, or gustatory organ taste, or gustative object
• body, or tactile organ body-impression, or tactile object
• mind-base, or consciousness mind-object (manāyatana, dhammāyatana)

“By the visual organ (cakkhāyatana) is meant the sensitive part of the eye (cakkhu-pasāda) built up of the four elements … responding to sense-stimuli” sa-ppaṭigha)… Vibhaṅga II

Similar is the explanation of the four remaining physical sense-organs.

Mind-base (manāyatana) is a collective term for all consciousness whatever, and should therefore not be confounded with the mind-element (mano-dhātu; see dhātu II, 16), which latter performs only the functions of adverting (āvajjana) to the sense-object, and of receiving (sampaṭicchana) the sense-object. On the functions of the mind, see viññāṇa-kicca.

The visible object (rūpāyatana) is described in Vibhaṅga II as “that phenomenon which is built up of the four physical elements and appears as color, etc.” What is' seen by-visual perception, i.e. by eye-consciousness (cakkhu-viññāṇa) are colors and differences of light, but not three dimensional bodily things.

'Mind-object-base' (dhammāyatana) is identical with 'mind-object-element' (dhamma-dhātu; see dhātu II) and dhammārammaṇa (see ārammaṇa).

It may be physical or mental, past, present or future, real or imaginary.

The 5 physical sense-organs are also called faculties (see indriya), and of these faculties it is said in MN 43:

“Each of the five faculties owns a different sphere, and none of them partakes of the sphere of another one; … they have mind as their support… are conditioned by vitality, … but vitality again is conditioned by heat, heat again by vitality, just as the light and flame of a burning lamp are mutually conditioned.”

The 12 bases are fully discussed in Visuddhi Magga XV. In Yam III (s F. Guide, p 98f) the 12 terms are subjected to a logical investigation The six personal bases form the 5th link of dependent origination (see paṭiccasamuppāda 5).