Buddha Abhidhamma - Ultimate Science - BuddhaNet

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Nibbàna is Khandha-vimutti
In the classification of five groups of existence, Nibbàna is not
included. The reason is that there is only one Nibbàna and it
belongs to a class of its own. As it always exists, it cannot be
differentiated as past, present and future. It cannot be differentiated
as internal and external – it belongs to the external
(bahiddha). It cannot be differentiated as base and supreme – it
belongs to the supreme (panãta). It cannot be differentiated as
dure (distant) and santike (near) –it is dure alone as it is far from
ordinary knowledge. It cannot be differentiated as gross and
subtle – it is subtle (sukhuma).
Bahiddha, sukhuma, panãta and dure do not imply different
Nibbànas – they are the different attributes of the same Nibbàna.
So there are no two varieties of Nibbàna. Thus Nibbàna need
not be classified as a khandha.
3 Twelve âyatanas (Twelve Bases)
‘âyatana’ means base, source or sphere. Here the twelve àyatanas
means the 12 bases or sources from which consciousness and
its concomitants arise.
The 12 bases are divided equally into two groups:
(a) ajjhattika (internal) and (b) bàhira (external).
a Ajjhattikàyatana (Six internal bases)
1 Cakkhàyatana – cakkhu-pasàda – eye-base (sensitive part
of the eye),
2 Sotàyatana – sota-pasàda – ear-base (sensitive part of the
ear),
3 Ghànàyatana – ghàna-pasàda – nose-base (sensitive part
of the nose),