Different objects can be experienced through different doorways (in Pāli :
dvāra). For example, the pasāda-rūpa in the eye (the rūpa which has the
capacity to receive visible object) is a necessary condition for citta to
experience visible object. If there were not pasāda-rūpa in the eye, citta could
not experience visible object.
Cittas of the sense-door process know their objects through the doors of the
eye, the ear, the nose, the tongue and the body-sense. As regards the door
of the body-sense, the pasāda-rūpa which has the capacity to receive bodily
impressions such as hardness, softness, heat, cold, motion or pressure, is any
part of the body which can receive such impressions. Thus, any part of the
body can be body-door, except those parts which have no sensitivity.
Five doors are rūpa and one door is nāma. The mind-door is nāma.
The cittas of the mind-door process experience an object through the mind-
door. Before the mano-dvārāvajjana-citta (mind-door-adverting-
consciousness) arises there are the bhavanga-calana (vibrating bhavanga)
and the bhavangupaccheda (arrest-bhavanga). The bhavangupaccheda,
the citta preceding the mano-dvārāvajjana-citta, is the mind-door. It is the
'doorway' through which mano-dvārāvajjana-citta experiences its object.
It is useful to know through which door cittas experience different objects. For example, visible object which is rūpārammana can be experienced both through the eye-door and through the mind-door. It is experienced through the eye-door when it has not fallen away yet. When it is experienced by the cittas of the mind-door process following upon that eye-door process, it has just fallen away. When visible object is experienced through the mind-door the cittas only know visible object, they do not think of a person or a thing. But time and again there are also mind-door processes of cittas which think of people or things and then the object is a concept, not visible object. The experience of visible object conditions the thinking of concepts which arises later on.