Buddha often said that in order to attain enlightenment one has to understand the Four Noble Truths; or similarly, one has to understand dependent origination. On the basis of the Buddha’s own statements, we can see a very close relationship between the Four Noble Truths and dependent origination. What is it that the Four Noble Truths and dependent origination have in common? The principle that both have in common is the principle of causality - the law of cause and effect, of action and consequence. The Four Noble Truths are divided into two groups.
The first two - suffering and the causes of suffering, and the last two - the end of suffering and the path to the end of suffering. In both of these groups, it is the law of cause and effect that governs the relationship between the two. In other words, suffering is the effect of the cause of suffering; and similarly, the end of suffering is the effect of the path to the end of suffering. Here too in regard to dependent origination, the fundamental principle at work is that of cause and effect. In dependent origination, we have a more detailed description of what actually takes place in the causal process.
Let us take a few examples that establish the nature of dependent origination. Let us take first an example used by the Buddha Himself. The Buddha has said the flame in an oil lamp burns dependent upon the oil and the wick. When the oil and the wick are present, the flame in an oil lamp burns. If either of these is absent, the flame will cease to burn.
This example illustrates the principle of dependent origination with respect to a flame in an oil lamp. Let us take the example of the sprout. Dependent upon the seed, earth, water, air and sunlight the sprout arises. There are in fact innumerable examples of dependent origination because there is no existing phenomenon that is not the effect of dependent origination. All these phenomena arise dependent upon a number of causal factors. Very simply, this is the principle of dependent origination.
Particularly, we are interested in the principle of dependent origination as it applies to the problem of suffering and rebirth. We are interested in how dependent origination explains the situation in which we find ourselves here. In this sense, it is important to remember that dependent origination is essentially and primarily a teaching that has to do with the problem of suffering and how to free ourselves from suffering, and not a description of the evolution of the universe.
Let me briefly list the twelve components or links that make up dependent origination. They are ignorance, mental formation, consciousness, name and form, the six senses, contact, feeling, craving, clinging, becoming, birth, and old age and death.
There are two principal ways in which we can understand these twelve components. One way to understand them is sequentially, over a period of three lifetimes: the past life, the present life and the future life. In this case, ignorance and mental formation belong to the past life. They represent the conditions that are responsible for the occurrence of this life. The following components of dependent origination - consciousness, name and form, the six senses, contact, feeling, craving, clinging and becoming - belong to this life. In brief, these eight components constitute the process of evolution within this life.
The last two components - birth and old age and death - belong to the future life. According to this scheme, we can see how the twelve components of dependent origination are distributed over the period of three lifetimes, and how the first two - ignorance and mental formation result in the emergence of this life with its psycho-physical personality and how in turn, the actions performed in this life result in rebirth in the future life. This is one popular and authoritative way of interpreting the twelve components of dependent origination.