If one has not diligently trained the Citta of the Sensual Realm, Then the Form Realm Citta cannot arise. Concerning the training of the Sensual Realm Citta, one must first of all thoroughly know it and one must question where the Sensual Realm comes into being.

The Sensual Realm arises dependent on the six sense-doors. The five sense-doors (Panca-Dvara) which include the eye, ear, nose, tongue and body, only receive present objects and cannot receive objects of the past or future. But the Mind-Door (Manodvara) receives objects of the past or present.2
Furthermore, one who is going to practise meditation should know about the "Passive Citta" (Bhavahga-Citta) and the "Active Citta" (Vithi-Citta).3 The Active Citta is that which receives information from the six sense doors. When the Citta ceases to receive information from the six sense doors, it then becomes the Passive Citta which is present at such times as during deep sleep.

The Sense Doors and the States Free of Doors

In addition to the above, one must have an understanding of the "Doors of Sense" (Dvara Sarnmuti) and the "States Free of Doors" (Dvara Vimutti). The "Doors of Sense" , refers to the activity of the six sense doors; whereas "States Free of Doors" , refers to such times as during Dream States, when one sees various
things in a dream. The nature of this state is that of the Citta being free of the sense doors. As it is said; the state free of the sense doors arises beyond the scope of the six sense doors and performs the function of " Descending, Re-linking, and establishing the Passive State (Cuti, Patฺisandhi, Bhavanga), based upon one of
the six types of objects which were received into the sense doors in the past as Kamma forming consciousness of the Sensual Realm (Kamavacara-Javana), and which arises in the "Process close to the time of Death" (Maranฺasanna-vithi).
Starting with the past life, whatever thing is established as the object of the Citta at the time of Re-linking, that same thing becomes established as the object of the Passive State in the present life.
The object which arose in the "Process close to the time of Death" , in the past life, was either a "Present Object", a "Past-Object", or a "Concept" (Pannatti). The Buddha called them Kamma, Kamma Nimitta (Symbol of Kamma) and Gati Nimitta (Representation Symbol).

The Citta which receives pleasing and displeasing objects in the five sense-doors is called the Twice-Fivefold-Consciousness (Dvipanca-vinnanฺa),1 making in all, Ten Types of Consciousness. These are associated with the five types of Objects such as Visible-Form (Rupa), and so on for the remaining types of sense objects.

With regard to the Threefold-Mind-Element (Manodhatuttikam),2 it grasps at the five types of object by which it is conditioned (Arammanฺa-Paccaya). When they arise in the Sense-door Process (Dvara-Vithi), each of these five types of consciousness are conditioned by their object. (Thus, Eye Consciousness is conditioned by Sight objects).

1.The types of Resultant -Consciouseness -of-the-Sensual-Realm, (Kamava-cara-Vipaka), thus include :

a) Investigating Consciousness (Santirana) 3 types.

b)The "Great-Resultant" Types (Maha-Vipaka) 8 types.

c)Joyful Mind-Consciousness-Element (Hasituppada) 1 type.

d)Twice Fivefold Sense Consciousness (Dvipancavinnanฺa)10 types.

e)Mind-Element (Manodhatu) 3 types.

Total : 25 types.