This is a complex topic. I will summarize the main points related to your questions.
1. Everything in this world (living and lifeless) is made of pure octads (suddhāṭṭhaka.) A pure octad is made of eight components, as I described above. It is a complex account, but all eight components have “seeds” in mental power.
- Four arise due to avijja (ignorance about Buddha’s teachings), and the other four due to craving (tanha). Defiled minds create them with rage, dosa, and avijja. See “The Origin of Matter – Suddhāṭṭhaka.”
- It may seem impossible, but it can be explained in detail with a good background in Abhidhamma.
2. The proportions of the eight components define an infinite variety of inert things in the world. For example, rocks primarily have the pathavi component, and water primarily has the apo component. On the other hand, sugar would have pathavi (giving hardness) and rasa (giving sweetness.)
- I provided brief explanations in “Buddhist Theory of Matter – Fundamentals” and “The Origin of Matter – Suddhāṭṭhaka.”
3. Lagrade wrote, “I’ve read that the essence of a human (and animal) is in the gandhabba which contains 6 pure octads (for 5 pasada rupa and hadaya vatthu).”
- That is correct. Thus, a gandhabba is primarily made of six suddhāṭṭhaka.
- But they have two other components each to make them “alive.” Here, a suddhāṭṭhaka combines with a jivita rupa and another unit created by kammic energy to become a dasaka.
- P.S. The jivita rupa component is in all “live entities” and the tenth component carries out a specific task.
- For example, a cakkhu pasada (together with the other nine units) creates a cakkhu dasaka responsible for seeing. That tenth component of cakkhu pasada makes it possible to “see.” The tenth component in the seat of the mind, hadaya vatthu, makes it able to create thoughts (citta.) See “Rupa Kalāpa (Grouping of Matter)” for some details.
- Those basic kammic laws cannot be explained further. They are nature’s laws, just like laws of gravity. Like scientists discover the laws of gravitation, a Buddha discovers the laws of kamma.
- The laws of kamma make it possible for cakkhu pasada rupa “to see,” or a hadaya vatthu to become the “seat of the mind,” for example.
4. As explained in #3 above, Our mental body is the gandhabba, made of six types of dasaka.
- That is where all the “action” takes place. Our physical sensory faculties (like the eyes, nose, etc.) are only the “doors” to the external world. The brain processes the signals coming through them and passes them over to the corresponding pasada rupa.
- That is explained in “Brain – Interface between Mind and Body.”
- When the gandhabba comes out of a physical body (as in NDE or OBE), a gandhabba can see, hear, etc., on its own. See “Near-Death Experiences (NDE): Brain Is Not the Mind” and “Manomaya Kaya and Out-of-Body Experience (OBE).”
This is a complex subject. One needs to have a good knowledge of Abhidhamma to fully understand, but one should be able to get the general idea.