A Basic Foundation in Buddhism Part 4:
The Noble Truth of the Cessation of Suffering (滅諦; mettai).
The previous two truths covered put forward the truth of the realm of delusion. The next two truths, in contrast, put forward the truth of the realm of wakefulness. Insight into the origin of suffering leads us to absolute peace (安住; anju), which is the truth of cessation. In other words, the result of awakening is the truth of cessation and the cause of awakening is the truth of a path. In this way, the four noble truths teach us cause and effect, which can be looked at in regular order and in reverse; suffering (effect); arising (cause), cessation (effect); path (cause). The explanation of the effect before the cause is characteristic of Buddhist texts. This is because regular block-heads like me are unlikely to respond if the cause is explained first. Unless we can demonstrate nirvana (涅槃; nehan) which is cessation, we will not be interested in embarking on the path to get there.
It is said that nirvana, which is the truth of cessation, is the ultimate realm of wakefulness which Buddhists aspire to. This goal is often described in terms of 'nirvana' (涅槃; nehan) rather than 'cessation' (滅; metsu). We often hear the phrase 'entering nirvana' (涅槃に入る; nehan-ni-hairu) or 'facing nirvana' (涅槃に向う; nehan-ni-mukou). These phrases however are both translations of the original meaning, which is 'cessation'. There are other ways of expressing this, such as 'tranquility/extinguishment' (円寂; enjaku), however the literal translation of this term means 'to blow out the flame' or 'the condition of being blown out'.
According to the Āgama sutras (阿含經; agonkyō), nirvana is the extinguishment of ignorance, aversion and craving. This reveals a condition by which the fires of the kleśās are put out, and in which the cause and effect between life and death is extinguished. The realm of absolute peace termed 'nirvana' is one in which the cause and effect between life and death (the truth of the arising of suffering and the truth of the cessation of suffering) is extinguished. Extinguishing the cause and effect between life and death means there is no longer the endless cycle of rebirth.
The realm of life and death is a realm of suffering and bewilderment. It is us ordinary beings who never stop repeating this cycle of life and death, being born and dying again and again. This cycle is referred to as 'the six realms of rebirth' (六道輪廻; rokudo-rinne). The six realms refer to the six realms in which beings live and die, that is, the hell realm, the hungry ghost realm, the asura realm, the human realm, and the celestial (heavenly) realm. What is the cause of this cycle? It is nothing other than the three-root poisons of ignorance, aversion and craving. Having the mind of these three poisons is what produces the path of the six realms moment by moment. This is the cause and effect of life and death. Therefore, when these three root fires are extinguished the cause of life and death amidst the realm of delusion is extinguished. This is what we call nirvana, or extinguishment.
The above is a general overview of nirvana, however as I mentioned previously, nirvana is interpreted in various ways across the development of Buddhist thought. Mahayana Buddhism for example teaches the nirvana of non-abiding (無住處涅槃; mujūsho-nehan) in which one enters the realm of samsara without permanent abode (無住處; mujūsho) out of great compassion for the sake of all beings (衆生救濟; shūjō-kusai). With this in mind, I would like you to understand that there is not only one interpretation and that referencing the term nirvana can mean various things.
