1. Rupa (or matter) can be generated by four causes: kamma, citta, utu, and Ahara (food). I will discuss these in detail later.
- Kamma here refers to volition (cetana). The 25 kinds of kamma that produce rupas are the volitions of the 12 akusala cittā, 8 great kusala cittā, and the five rupaloka kusala cittā. These rupa are created with a time lag, when kamma vipāka bear fruits, like at the patisandhi to a new life. The three rupa dasaka of vatthu, kaya, and bhava are created at patisandhi by kamma vipāka.
- The rupa produced by the cittā arise at the same time as the citta themselves, and only at the rising part of the cittā. Out of the 89 possible cittā, 75 cittā can produce rupa (4 arupaloka vipāka cittā and the two sets of fivefold sense consciousness cannot produce rupa).
- Thus both kammaja and cittaja rupa have mind as the direct cause. Both of these decay rapidly and are converted to utuja rupa. What we normally see are the utuja rupa and aharaja rupa, which have their origins also in the great elements of tejo and oja.
- The great element tejo is responsible for producing utu samutthana rupa: Beginning from the moment of rebirth-linking, the internal tejo element found in the rupa kalapas born of kamma combines with the external tejo and starts producing organic material phenomena originating from tejo. Thereafter the tejo element in the rupa kalapas born of all four causes produces organic material phenomena born of tejo element throughout the life. Externally, tejo element also produces inorganic material phenomena, such as climatic and geological transformations.
- The nutritive essence, oja, is present in all rupa-kalapas both inside the body (internal) and outside the body (external). The external food, which is eaten, is digested in the stomach and dispersed through blood to all parts of the body. So the internal oja and the external oja meet in every part of the body. The combination of internal and external oja produce aharaja rupas.
2. The 8 rupas of patavi, apo, tejo, vayo, vaṇṇa, gandha, rasa, and oja are ALWAYS found together. That unit or kalapa is the smallest rupa unit and is called the pure octad (suddhashtaka).
3. The four lakkhana rupas of upacaya, santati, jarāta, and aniccata are not produced by any cause. They represent the nature of rupas.
4. The remaining 15 rupa are produced by different combination of the four possible causes as shown in the table below:
|Kamma Born||Citta Born||Utu Born||Ahara Born|
|Itthi Bhva (femininity)||Yes|
|Hadaya vatthu (heart base)||Yes|
|Jivitindriya (life faculty)||Yes|
|Kaya vinnati (bodily intimation)||Yes|
|Vaci Vinnati (vocal intimation)||Yes|