1. 'spheres', is a name for the four immaterial absorptions; s. jha^na (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 (ba^hira) 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
"By the visual organ (cakkha^yatana) is meant the sensitive part of the eye (cakkhu-pasa^da) built up of the four elements ... responding to sense-stimuli" (sa-ppatigha).... (Vibh. II). Similar is the explanation of the four remaining physical sense-organs.
Mind-base (mana^yatana) is a collective term for all consciousness whatever, and should therefore not be confounded with the mind-element (mano-dha^tu; s. dha^tu II, 16), which latter performs only the functions of adverting (a^vajjana) to the sense-object, and of receiving (sampaticchana) the sense-object. On the functions of the mind, s. vin~n~a^na-kicca.
The visible object (rúpa^yatana) is described in Vibh. 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-vin~n~a^na) are colors and differences of light, but not three dimensional bodily things.
'Mind-object-base' (dhamma^yatana) is identical with 'mind-object-element' (dhamma-dha^tu; s. dha^tu II) and dhamma^rammana (s. a^rammana). It may be physical or mental, past, present or future, real or imaginary.
The 5 physical sense-organs are also called faculties (indriya, q.v.), and of these faculties it is said in M. 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 Vis.M. XV. In Yam III (s Guide, p 98f) the 12 terms are subjected to a logical investigation The six personal bases form the 5th link of dependent origination (paticca-samuppa^da 5, q.v.).