The standard formula of dependent origination (paṭiccasamuppāda) is given in SN 12.1. The definition of every nidana is given in SN 12.2.
In the standard formula of dependent origination, every nidana that comes after, depends on the one that comes before, as the condition for arising. When the nidana before ceases, the nidana after ceases too.
Ignorance or avijja is the force of nature that gives rise to the mind-body phenomena, and also gives rise to the underlying tendencies that drive us towards craving. It's the natural or evolutionary instinct that drives us towards survival, sensual enjoyment and individual existence.
Dependent on ignorance, volitional formations (sankhara) arises. These are the physical and mental processes. The physical processes here refers to breathing and the rest of the processes like heart beating etc. (i.e. kaya sankhara). Mental processes are of two types. One is the "input path" which processes inputs (the six types of feelings) and produces mental states or cittas (i.e. citta sankhara), while the other is the "output path" which produces actions and words (i.e. vaci sankhara). This is based on MN 44.
Dependent on volitional formations, consciousness (vinnana) arises. SN 35.93 tells us that dependent on eyes and form, eye-consciousness arises. The six types of consciousness are related to the six sense media.
The way I see it, consciousness is the mind-body connection (where mind is "name" and body is "form"), and it's supported by:
Name, reverends, is one end. Form is the second end.
Consciousness is
the middle. And craving is the seamstress,
for craving weaves one to
being reborn in one state of existence or another.
AN 6.61
For all six senses, consciousness is also like the mental instrument of focus. We get many sensory input all the time from the six senses. Consciousness is used to focus on something. The sutta below says that intention, planning and underlying tendencies (obsessions) would determine where consciousness would land upon and grow. Even if one does not intend or plan, but still has underlying tendencies, consciousness will still land upon and grow there.
“Mendicants, what you intend or plan, and what you have underlying
tendencies for become a support for the continuation of consciousness.
When this support exists, consciousness becomes established. When
consciousness is established and grows, there is rebirth into a new
state of existence in the future.
If you don’t intend or plan, but still have underlying tendencies,
this becomes a support for the continuation of consciousness. When
this support exists, consciousness becomes established. When
consciousness is established and grows, there is rebirth into a new
state of existence in the future.
SN 12.38
Dependent on consciousness, name-and-form (namarupa) arises. Name-and-form represents a mind-body system that operates together, like software-and-hardware. And if you read the definitions of "name" (feeling, perception, volition, contact, attention) and "form" (form made up of four great elements), they read like definitions of parts of mind and body respectively.
The body is called "form" because it is the form-sensor, that senses external forms. The mind is called "name" because it is the name-assigner, that assigns names to the forms sensed by the body. So the terms name(-assigner) and form(-sensor) describe functions of the mind and the body in the combination of namarupa.
Name-and-form (mind-body) has a mutually dependent relationship with the six types of consciousness according to SN 12.67, like two sheaves of reed leaning on each other.
To put it another way, the mind-body system (name-and-form) depends on the mind-body connection (consciousness) and the mind-body connection (consciousness) depends on the mind-body system (name-and-form).
The nidana of sankhara that comes before consciousness, is defined as bodily formations, verbal formations and mental formations. These represent the basic functioning or basic operations of the body and the mind, as separated or independent operations. Then when body and mind connects, we get consciousness which gives rise to the mind-body system and the mind-body system in turn sustains consciousness.
Depending on name-and-form (mind-body system), the six sense bases (salayatana) arises. And then dependent on the six sense bases, contact (phassa) arises. And then dependent on contact, feeling (vedana) arises.
SN 35.93 tells us that dependent on eyes and form, eye-consciousness arises. Then, the meeting of the three (eye, forms, eye-consciousness) gives rise to eye-contact. Eye-contact gives rise to feeling (sensation) born of eye-contact. The same applies to the other sense media and their objects of sensation.
So, consciousness here, is the mind-body connection. Eye-consciousness plus the physical eye, gives rise to the eye base. And similarly for the rest of the sense bases. The six sense bases refer to the six sense organs working with the six sense-consciousness (mind-body connections).
Contact is the meeting of the three - eye, eye-consciousness and forms, or you can say it's the eye base meeting forms. Then this gives rise to feeling (vedana), which is the mental input captured from the sense media.
I see the six sense bases as the six types of consciousness scanning the input of the six physical sense media through the mind-body system. Then when they meet the six types of sense objects, we get the six types of contacts.
Feeling (vedana) which is the mental input based on the six sense media contacts are then identified by the faculty of perception (sanna) based on memory, and then thoughts are produced based on concept proliferation/ objectification-classification/ reification (papanca). How this works is explained in this answer with details about the train of thought arising from papanca by the mechanisms of vitakka and vicara. All this takes place in the mind (nama) part of the mind-body system (namarupa).
Also:
What one feels, one perceives. What one perceives, one thinks about.
What one thinks about, one mentally proliferates. What a person
mentally proliferates is the source through which perceptions and
notions due to mental proliferation impacts one
regarding past, future
and present forms cognizable through the eye."
MN 18
Next, dependent on feelings, craving (tanha) arises. Craving is a habit of reification (papanca) as explained in this answer. Reification or papanca is explained in this answer. There are 3 types of craving - sensual, becoming and non-becoming.
Clinging (upadana) arises dependent on craving. That's when the mind is attached to what it has experienced before, with respect to sensual pleasures and views. The mind has constructed likes and dislikes.
Existence or becoming (bhava) arises dependent on clinging. That's when the mind constructs worlds of mental formations (please see this answer), or perhaps you can call it mental realities. For e.g. a rich person may have a different mental world from a poor person. A man may have a different mental world from a woman. A person staying in one country may have a different mental world from a person staying in another country. Now, people are living with the mental reality of the Covid pandemic, which is a mental existence.
Then this gives rise to the birth (jati) of the mental idea of the self, or individual identity, for e.g. the mental identity of a rich white man by the name of "James", living in Canada, who works as a lawyer, and is married etc. Please see this answer. Here, we can tell the story of the "carrier of the burden" (SN 12.22) by the name of "James", how he was born, how he grew up etc.
The birth of the mental idea of the self gives rise to the rest of suffering i.e. aging, disease and death (jara-marana). "Death" here refers to the fear or terror of death, of the individual identity (e.g. "James"). An arahant (fully liberated one) becomes deathless, meaning he becomes free from the fear and terror of death of individual identity. Also partially covered by this answer.
What about rebirth?
That refers to the cessation of the old mental individual identity and the arising of the new mental individual identity, from one mind-moment to the next mind-moment. The mind-moments cease and arise along with contact. So, this happens when one contact ceases and a new one arises. Craving is what sustains the continuity from one mental individual identity to the next.
Contact, reverends, is one end. The origin of contact is the second
end. The cessation of contact is the middle. And craving is the
seamstress, for craving weaves one to being reborn in one state of
existence or another.
Identity, reverends, is one end.
The origin of identity is the second
end. The cessation of identity is the middle. And craving is the
seamstress, for craving weaves one to being reborn in one state of
existence or another.
AN 6.61
“When a being has laid down this body but has not yet been
reborn in another body, I declare that it is fuelled by craving. For
on that occasion craving is its fuel.”
SN 44.9
Please read this answer (south indian monkey trap) which explains the connection between ignorance and suffering, as well as why cultivation of wisdom is needed, to weaken ignorance, to diminish craving, which reduces suffering.
For the arahant (fully liberated one), please see this answer. Here, ignorance, craving, clinging, becoming or existence, birth and the rest of suffering are fully extinguished. However, for the living arahant, the five aggregates (and therefore also volitional formations, consciousness, name-and-form, six sense bases and feelings) are still operating without craving or clinging, and without burning with the fires of passion, aversion and delusion. When the arahant passes away, all of these ceases.
