The Buddhist theory of Dependent Origination is centered around the problem of human life. there are, it is generally believed, ten or twelve Links of Dependent Origination. The twelve links are: Ignorance, Mental Formation, Consciousness, Name and Form, Six Sense Organs, Contact between sense organs and sense objects, Sensations, Desire, Clinging, Coming into Existence, Birth, and Old Age and Death. Let me explain them briefly:
⑴ Old Age and Death: This is the starting point from which to observe an individual’s life. Old age, death, worrying and sorrow are inevitable in a person’s life. What is the origin of aging, death, sorrow and worrying? It is ⑵ Birth. If a person is not born there are on old age and death, nor sorrow and worrying. Though the conditions for birth are numerous, the most important one is ⑶ Process of coming into existence (Brava, meaning existence). In brief, bhava is a kind of latent force of kamma, birth and death are the inevitable outcome. What is the condition for Bhava’s arising” It is ⑷ Grasping or Clinging (Upadana). Upadana means craving and clinging, craving for visible objects, for sounds, odors, tastes, and tangible objects, clinging to the possetion of lovely things. This is grasping. Because of this self-centered grasping and clinging, activities of body, speech and mind are produced. Grasping arises from ⑸ Desire (Tanha). Tanha can be simply explained as the desire for existence or survival. It is the driving force of the activities of life. It is this desire for life that leads to grasping and clinging, which bring about the activities of body, speech and mind, which from the force of kamma that results in birth and death. Therefore, Tanha, Upadana and Bhava together are said to be the causes of birth and death. The above explains the cause-and-effect relationship between illusion, kamma and suffering. In order to further investigate the origin of the desire for life, it is necessary to explain the relationship between ⑹ Sensation (Vedana), ⑺ Contact (Phassa) and ⑻ Six Sense Organs. Sensation refers to the feelings associated with the objective existence which can be classified into three groups: pleasant, unpleasant and neither pleasant nor unpleasant. When pleasant and unpleasant sensations are experienced, the desire for existence is stimulated and given impetus. Sensation is the response to the stimuli of the outside world. Thus it depends on contact between the sense organs and sense objects. Contact is thus the starting point of the mental coordination of sense organs, sense objects. Contact is thus the starting point of the mental coordination of sense organs, sense objects and consciousness. Take, for example, the eye contact with the red color (object). When the red color stimulates the eye, the eye consciousness, which is in charge of vision, comes into play. With the interaction of organ, object and consciousness, contact with (reaction to) red color occurs. In this way, contact depends upon the six sense organs. The six sense organs are eye, ear, nose, tongue, body and mind, which have functions of perceiving the six sense objects, namely, visible objects, sound, odor, taste, tangible objects and dhamma (Dhamma here refers to the impression left from the first five elements, or the object of the mental organ).
Furthermore, when investigation is made concerning the origin of the six sense organs, we come to ⑼ Name and Form (Nama-rupa). The meaning of nama-rupa, as mentioned above, is the composition of body and mind (for the five aggregates). The existence of the six sense organs is dependent upon the whole body and mind, or in other words, nama-rupa is the basis of the six organs. What condition does nama-rupa depend upon? It depends upon ⑽ Consciousness (Vinnana). Consciousness is a part of nama-rupa. But when the nama-rupa is taken as the object of comprehension, consciousness becomes the kernel of the nama-rupa. Consciousness has the functions of recognition and judgment with relation to the objects, which thus make the objects more distinctive, and enhance the abilities of the organs, so that the sensations, perceptions and speculation are governed. Therefore, the unity of body and mind depends upon consciousness, consciousness in turn depends on body and mind. Consciousness can not stand alone without the functioning nama-rupa because its occurrence is based on the stimuli of the objects to the sense organs and the help of sensations, perceptions and speculations. In conclusion, nama-rupa and vinnana have a relation of mutual dependence.
The foregoing discussion was of the ten links of Dependent Origination. With regard to the present activities of human beings, the ten links of Dependent Origination would be quite comprehensive. However, to explain the endless cycles of birth and death, two more links, Mental formation and Ignorance must be added. Together with the above ten, they constitute the twelve Links of Dependent Origination.
⑾ Mental formation has the same meaning as ⑶ Existence (Bhava). When considering the Kamma created by body, speech and mind in the present, it has a potential power to lead to the future fruit that is known as “Bhava” (“coming into existence”). Whereas, when considering the ripe fruit (result) of today, what was formed by past kamma (or actions) is known as “Sankhara” (“formation”). Consciousness and the name and form are the ripe fruits of today, depending upon the past formations. Owing to the cycles of past “formations” with its beginning unknown, habit becomes second nature. Just as there is a latent power governing human beings’ actions, so the phenomena of birth and death, suffering and worrying occur endlessly. Sankhara in turn depends on ⑿ Ignorance. Ignorance refers to being unable to see things as they actually are, or unable to see the reality of impermanent and selfless dhammas which arise when the conditions arise and cease when the conditions cease. An ignorant person especially does not understand the fact that one’s own body and mind are merely formed by causes and conditions, while he holds the idea that there is an eternal, unique and dominant self. Because of the affirmation of “self”, he feels the sensations of pleasant, unpleasant and neutral, and thus has the afflictions of greed, hatred and ignorance, which result in various wholesome and unwholesome kammas. Therefore, the root cause of the sufferings of birth and death of human beings lies in Ignorance.
To sum up, the twelve Links of Dependent Origination are no more than the relationships between illusion, kamma and suffering. Ignorance and mental formations are the result of the illusions and kammas form the endless past, which have incurred the present bitter fruits of consciousness, name and form, six sense organs, contact, and sensation. Desire, grasping and becoming existence are the present illusions and kammas, which will lead to the future bitter fruits of birth, aging and death. All these mentioned above are implied in the sentence “All asavas are suffering”, which also covers “the Truth of Suffering” and “the Truth of the origin of Suffering”—two of the four “Noble Truths”. (From Essentials of Buddhism: Questions and Answers)