The main factors
The standard form for presenting the principle of Dependent Origination is quite complex, more a matter for the specialist than for the casual reader. It requires an extensive foundation in Buddhism and a comprehensive vocabulary of Pali terms to thoroughly understand it. There are also scriptures devoted exclusively to the subject. Here I will briefly summarize the basic factors.
The main factors 
The main factors have already been covered in the Overview, so here they will be mentioned in brief only, given first in the Pali language, and followed by definitions of the Pali terms in English:
Avijja => sankhara => viññana => namarupa => salayatana => phassa => vedana => tanha => upadana => bhava => jati => jaramarana ... soka parideva dukkha domanassa upayasa => The cause of suffering (dukkha samudaya).
The division on cessation proceeds according to the same headings.
Because the principle of Dependent Origination revolves in the form of a cycle, beginningless and endless.
1. Avijja = Unknowing, or ignorance of dukkha, its cause, its cessation, and the way leading to its cessation (the Four Noble Truths); and, according to the Abhidhamma, not knowing what went before (the past), what comes after (the future), what came both before and after (the past and the future), and the principle of Dependent Origination.
2. Sankhara = Volitional Impulses: bodily formations, or intentional actions; verbal formations, or intentional speech; mental formations, or thoughts; and, according to the Abhidhamma: meritorious formations, or good kamma (puññabhisankhara), non-meritorious formations, or bad kamma (apuññabhisankhara), and fixed or unmoving formations, or special meritorious kamma (aneñjabhisankhara).
3. Viññana = Consciousness through eye, ear, nose, tongue, body and mind (including the re-linking consciousness, patisandhi viññana). (The six consciousnesses.)
4. Namarupa = Body and Mind: nama (name or mind): feeling, perception, intention, contact, attention, or, according to the Abhidhamma: the khandhas of feeling, perception and volitional impulses; and rupa (body or materiality): the four elements, earth, water, wind and fire and all forms dependent on them.
5. Salayatana = The six sense bases: eye, ear, nose, tongue, body and mind.
6. Phassa = Impingement or contact: eye contact, ear contact, nose contact, tongue contact, body contact and mind contact.
7. Vedana = Feelings (of pleasure, pain and indifference) arising from impingement on eye, ear, nose, tongue, body and mind.
8. Tanha = Craving for sights; craving for sounds; craving for odors; craving for tastes; craving for bodily sensations; craving for mind objects: the six cravings.
9. Upadana = Clinging to sense objects (kamupadana), that is, sights, sounds, odors, tastes and bodily sensations; clinging to views (ditthupadana); clinging to rules and practices (silabbatupadana); clinging to the concept of self (attavadupadana).
10. Bhava = Becoming, the conditions which lead to birth; also realms of existence: the sense realm (kamabhava); the realm of form (rupabhava); the realm of formlessness (arupabhava).
An alternative definition: Kammabhava, the realm of action, or actions which condition rebirth: meritorious actions (puññabhisankhara); demeritorious actions (apuññabhisankhara); imperturbable actions (aneñjabhisankhara); and Upapattibhava, the realms of rebirth: the sense realm; the realm of form; the formless realm; the realm of perception; the realm of non-perception; the realm of neither perception nor non-perception.
11. Jati = Birth, the arising of the khandhas and the sense bases, birth; the appearance or arising of things (this latter interpretation used in explaining the Dependent Origination cycle in one mind moment).
12. Jaramarana = Aging and death: jara: the aging process, the fading of the faculties; and marana: the breaking up of the khandhas, the dissolution of the life principle, death; alternatively, the dissipation and dissolution of phenomena.
Here are some examples of these general headings:
(Asava) =>Avijja -- Ignorance: Believing that this very self will be reborn in various states due to particular actions; that after death there is nothing; that life is a random process in which good and evil actions bear no fruit; that simply by adhering to a certain religion one will automatically be 'saved'; that material wealth will provide true happiness ... From there ...
=> Sankhara -- Volitional Impulses: Thinking and intending in accordance with those beliefs; considering and planning actions (kamma) in accordance with those intentions, some good, some bad and some neutral. From there ...
=> Viññana -- Consciousness: the perception and awareness of sensations, which will be related to particular intentions. Mind or consciousness is fashioned into specific qualities by intention. At death, the momentum of volitional impulses, propelled by the law of kamma, induces the so-fashioned re-linking consciousness (patisandhi viññana) to take a sphere of birth and level of existence appropriate to it. This is rebirth. From there ...
=> Namarupa -- Body and mind: The process of rebirth proceeds to create a life form primed to generate more kamma. As a result there are the rupa, vedana, sañña, and sankhara khandhas in their entirety, complete with the distinct qualities and defects endowed on them by the fashioning influence of conditions, or kamma, and constrained by the limitations of that particular sphere of existence (bhava), be it human, animal, divine, etc. ...
=> Salayatana -- The six sense bases: A sentient being must have the means to communicate with its environment in order to function and develop within it. Thus, supported by body and mind, and in conformity with kammic momentum, the organism proceeds to develop the six sense bases, the sense organs of eye, ear, nose, tongue, body and mind. From there ...
=> Phassa -- Contact: The process of awareness now operates through the contact or impingement of three factors. They are: the internal sense doors (eye, ear, nose, tongue, body and mind), external sense objects (sights, sounds, odors, tastes, bodily sensations and mind objects) and consciousness (eye-consciousness, ear-consciousness, nose-consciousness, tongue-consciousness, tactile-consciousness and mind-consciousness). Depending on this contact, there occurs ...
=> Vedana -- Feeling: The feelings, or the 'appreciation' of the qualities of sense contacts, be they of comfort (sukhavedana -- pleasant feeling), discomfort or pain (dukkhavedana -- unpleasant feeling) or indifference or equanimity (adukkhamasukha-vedana -- neutral feeling; or upekkhavedana -- equanimous feeling). In conformity with the nature of unenlightened beings, the process does not stop there, but goes on to ...
=> Tanha -- Craving: Comfortable feelings tend to produce liking and enjoyment, desire for and seeking after more of the same; for stressful feelings or discomfort there is displeasure, a desire to destroy or get rid of them. Neutral feeling in this context is considered to be a subtle form of pleasant feeling because it does not disturb the mind and invokes a certain amount of complacency. From here ...
=> Upadana -- Clinging: As desire intensifies, it becomes a holding onto or clinging to the object in question. As long as an object is yet unattained there is craving; as soon as the object is attained it is held fast by clinging. This refers not only to sense objects (kamupadana), but to ideas and views (ditthupadana), modes of practice or techniques (silabbatupadana) and the feeling of self (attavadupadana). On account of this clinging there follows ...
=> Bhava -- Becoming: Intention and deliberate action to produce and control things in accordance with the directives of clinging, leading to the further rotation of the whole process of behavior (kammabhava), being good kamma, bad kamma or neutral kamma, depending on the qualities of the craving and clinging which condition them. For example, one who desires to go to heaven will do those things which he or she believes will lead to rebirth in heaven, thus laying the groundwork for the five khandhas to appear in the realm (bhava) appropriate to those actions (kamma) (upapattibhava). With the process of creating kamma thus in full swing, one link gives rise to the next, which is ...
=> Jati -- Birth: Beginning with the re-linking consciousness, which is endowed with features contingent on its kammic momentum and connecting to a state appropriate to it, the five khandhas arise in a new life continuum, comprising name and form, the six sense bases, contact and feeling. When there is birth, what inevitably follows is ...
=> Jaramarana -- Aging and death: the decay and dissolution of that life continuum. For the unenlightened being these things are constantly threatening life in either overt or covert ways. Therefore, in the life of the unenlightened being, old age and death inevitably bring with them ...
=> Soka -- sorrow; parideva -- lamentation; dukkha -- pain; domanassa -- grief; and upayasa -- despair, which all in all can be summed up as simply 'suffering.' Thus we have in the final words of the principle of Dependent Origination formula: "Thus is the arising of this whole mass of suffering."
However, as the principle of Dependent Origination functions as a cycle, it does not stop there. The last factor becomes a crucial link in the further continuation of the cycle. Specifically, sorrow, lamentation and so on are all manifestations of the outflows. These outflows are four in number, namely: the concern with the gratification of the desires of the five senses (kamasava); attachment to views and beliefs, for example that the body is the self or belonging to self (ditthasava); desire for various states of being and the aspiration to attain and maintain them (bhavasava); and ignorance of the way things are (avijjasava).
Aging and death have an inflammatory effect on the outflows: in relation to kamasava they cause feelings of separation from the loved and cherished; in relation to ditthasava, aging and death confront the innate belief in self and attachment to the body; in relation to bhavasava, they mean separation from cherished states of being; in relation to avijjasava, lack of understanding on the fundamental level, (such as not understanding the nature of life, aging and death and how they should be related to), aging and death cause the unenlightened being to experience fear, melancholy, despair and superstitious grasping. These outflows are therefore the determinants for sorrow, lamentation, pain, grief and despair to arise as soon as aging and death appear.
Sorrow and suffering affect the mind in negative ways. Whenever suffering arises, the mind becomes confused and muddled. The arising of sorrow is thus commensurate with the arising of ignorance, as is written in the Visuddhi Magga:
'Sorrow, pain, grief and despair are inseparable from ignorance, and lamentation is the norm for the deluded being. For that reason, when sorrow is fully manifest, so also is ignorance fully manifest.' [Vism.576]
'As for ignorance, know that it arises with the arising of sorrow ...' [Vism.577]
'Ignorance is present as long as sorrow is present.' [Vism.529]
'With the arising of the outflows, ignorance is arisen.' [M.I.54]
Thus it can be said that for the unenlightened being, aging and death, together with their retinue -- sorrow, lamentation, pain, grief and despair -- are factors for producing more ignorance, thus turning the cycle once more.
The cycle of Dependent Origination is also known as the Wheel of Becoming (bhavacakka), or Wheel of Samsara. This model covers three lifetimes -- ignorance and volitional impulses are in one lifetime, consciousness to becoming are in a second lifetime, while birth and aging and death (with sorrow, lamentation and so on) occur in a third. Taking the middle life-span as the present one, we can divide the three life periods, with the entire twelve links of the Dependent Origination cycle, into three time periods, thus:
1. Past life -- Ignorance, volitional impulses:
2. Present life -- Consciousness, body and mind, sense bases, contact, feeling, craving, clinging, becoming:
3. Future life -- Birth, aging and death (sorrow, lamentation, pain, grief and despair).
Among these three periods, the middle period, the present, is our base. From this perspective, we see the relationship of the past section as purely a causal one, that is, results in the present are derived from causes in the past (past cause => present result), whereas the future section specifically shows results, that is extending from causes in the present to results in the future (present cause => future result). Thus the middle section, the present, contains both causal and resultant conditions. We can now represent the whole cycle in four sections:
1. Past cause = Ignorance, volitional impulses:
2. Present result = Consciousness, body and mind, sense bases, contact, feeling.
3. Present cause = Craving, clinging, becoming:
4. Future result = Birth, aging and death (sorrow, lamentation, etc.).
Some of the links in this chain are related in meaning, and they can be grouped as follows:
1. Ignorance and craving-clinging
From the description of ignorance (avijja), it appears that craving (tanha) and clinging (upadana) are involved, especially the clinging to self, which is present throughout. Not knowing the truth of life, and mistakenly believing in a self, leads to craving on behalf of that self, together with its various forms of clinging. In the words 'With the arising of outflows there is the arising of ignorance,' kamasava (the outflow of sensual desire), bhavasava (the outflow of desire for being) and ditthasava (the outflow of attachment to views) are all types of craving and clinging. Thus, when speaking of ignorance, the meaning invariably includes craving and clinging.
The same applies to any descriptions of craving and clinging -- ignorance is always connected to them. The deluded assumption of conditions to be real entities is the determinant for any wanting and clinging that arise. The more craving and clinging there are, the more is discernment cast aside and mindfulness and rational behavior impaired. Thus, when speaking of craving and clinging, ignorance is automatically implied.
In this light, ignorance as a past cause, and craving and clinging as present causes, mean much the same thing. But ignorance is classed as a past determinant, while craving and clinging are classed as present determinants, to show each of those factors in its prominent relationship with the other factors in the Wheel of Becoming.
2. Volitional impulses and becoming
Volitional impulses (sankhara) appear in the past life segment while becoming (bhava) occurs in the present life segment, but each plays a decisive role in the realm, or bhava, life is to appear in, and so they have similar meanings, differing only in their emphasis. Sankhara refers specifically to the factor of intention (cetana), which is the predominant factor in the creation of kamma. Bhava has a broader meaning, incorporating both kammabhava and upapattibhava. Kammabhava, like sankhara, has intention as its principal motivating force, but it differs from sankhara in that it covers the entire process of the generation of action. Upapattibhava refers to the five khandhas arising as a result of kammabhava.
3. Consciousness to feeling, and birth, aging and death
The segment of the cycle from consciousness to feeling is the present life, described point by point in order to illustrate the cause and effect relationship of the factors involved. Birth, together with aging and death, are 'future results.' The cycle at this point tells us that causes in the present must generate future results, in this case aging and death. This is a repetition, in condensed form, of the consciousness to feeling segment of the cycle, emphasizing the arising and cessation of suffering. Aging and death also act as connecting points for a new cycle. It can be said, however, that the segments from consciousness to feeling, and from birth to aging and death, are virtually synonymous.
Bearing this in mind, the four stages of cause and effect can be divided thus:
1. Five past causes: Ignorance, volitional impulses, craving, clinging, becoming.
2. Five present results: Consciousness, body and mind, sense bases, contact, feeling (= birth, aging and death).
3. Five present causes: Ignorance, volitional impulses, craving, clinging, becoming.
4. Five future results: Consciousness, body and mind, sense bases, contact, feeling (= birth, aging and death).
Because of the relationship between the twelve links of the Dependent Origination cycle, they can be divided into three groups, called the vatta, or cycles.
1. Ignorance-craving-clinging (avijja-tanha-upadana) -- These are kilesa (defilements), the instigating forces for the various kinds of deluded thought and action. This section is accordingly called the kilesavatta.
2. Volitional impulses (sankhara, and rebirth conditioning actions ([[[kamma]]-] bhava) -- These are kamma, the process of action based on kilesa which conditions life. This segment is called the kammavatta.
3. Consciousness, body and mind, six sense bases, contact, feeling (viññana, namarupa, salayatana, phassa, vedana) -- These are vipaka, the events of life resulting from the effects of kamma. These then become food for kilesa, which then become the causes for the creation of more kamma. This segment is thus called the vipakavatta.
These three vatta are continuously propelling each other around in the cycle of life. Diagrammatically, they can be represented as in Figure 2.
Because defilements (kilesa) are the prime motivators of life conditions, they are positioned at the starting point of the cycle. Thus we can distinguish two starting points, or activating agents, in the wheel of life:
1. Ignorance is the agent from the past which influences the present up until feeling.
2. Craving is the agent in the present time, extending the cycle from feeling up until the future, aging and death.
The reason that ignorance appears in the former section while craving appears in the latter is because ignorance follows on from sorrow, lamentation, and so on, while craving follows on from feeling. Ignorance and craving are the predominant defilements in each respective case.
This model of the Dependent Origination cycle makes the following distinction in the ways rebirth takes place, depending on whether it is ignorance or craving (for being) that is the deciding factor:
Ignorance is the main cause of birth into woeful states, because the mind enveloped in ignorance is unable to distinguish between good and evil, right and wrong, useful and harmful. As a result there is no standard for behavior, actions are random and bad kamma is more likely to result than good kamma.
Craving for being (bhavatanha) is more likely to lead to birth in pleasant states. When it is the motivating force, there is an aspiration for a better station in life. As for future existences, the desire might be for rebirth in a heavenly or divine state. Where the present existence is concerned, the aspiration may be for wealth, fame, or reputation. Actions follow on from these initial aspirations. If the aspiration is for rebirth in a divine state, it may involve the development of refined meditation states; if the aspiration is for rebirth in a heavenly realm, then there may be maintenance of moral precepts and performance of generous actions; if the aspiration is for wealth, there may follow the industriousness required to that end; if the aspiration is for a good reputation, then there will be the performance of good works and so on. All of these actions must be based on a certain amount of self discipline, heedfulness and diligence. As a result, good actions are more likely to arise than with a life lived under the sole control of ignorance.
Although ignorance and craving for being have been placed at starting points in the cycle, they are not the prime movers of it. This is borne out by the Buddha's words:
"No beginning can be found, monks, to ignorance, thus : 'Before this point there was no ignorance, but then it arose.' In this case, it can only be said, 'Dependent on this, ignorance arises.'"
There are identical words for bhavatanha.
That ignorance and craving are major determinants and arise together in the process of Dependent Origination is borne out by the following quotation:
"Monks, this body, so arising in its entirety, whether to a fool or a wise man, enshrouded in ignorance and bound by craving, together with external physical and mental properties (namarupa), make two things. Dependent on these two things is impingement on the six sense bases. The fool or wise man, receiving impingement through one or other of those sense bases, experiences pleasure or pain." [S.II.23]
3. See Paccayakara-vibhanga, Vbh.135ff.; Vism.517-586; Vbh.A.130-213; Abhidhammattha-sangaha, Chapter 8.
4. For a reference to the descriptions given below, see S.II.2-4; Vbh.135; for commentary, see Vism.517-586; Vbh.A.130-213.
5. Pubbanta-aparanta-pubbantaparanta: the past, the future, both the past and the future.
6. Phassa is the contact between sense organ, sense object and consciousness.
7. Vedana can also be classified as three kinds: pleasant, unpleasant and neither pleasant nor unpleasant; or as five kinds: pleasant bodily feeling, unpleasant bodily feeling, pleasant mental feeling, unpleasant mental feeling, and neutral or indifferent feeling.
8. Craving can also be classified as of three kinds: sensual craving, craving for being and craving for annihilation. When these three are multiplied by the number of sense doors, six , there are eighteen; when again multiplied by two (internal and external) there are thirty-six; when this is again multiplied by three (past, present and future) the result is a total of 108 kinds of craving: A.II.212.
9. Vbh.145,159,191. This latter interpretation is used to explain the Dependent Origination cycle in one mind moment.
11. The three vatta are from the Commentaries. They explain the principle of Dependent Origination in a very simplified form: when there is kilesa, such as a desire to obtain something, it is followed by kamma, action to obtain it, and vipaka, the pleasant feeling that results on obtaining it or the unpleasant feeling that results from not obtaining it. These pleasant and unpleasant feelings cause the arising of more kilesa, more desire and aversion, which in turn generate more actions, kamma, leading to a different kind of vipaka, and so on.
12. A.V.113; Vism.525; according to this Sutta, ignorance is nurtured by the five hindrances.
13. A.V.116; Vism.525; craving for being is said to be nurtured by ignorance.