I opened the Buddhism dictionary of a specialist, and in the section of nirvana, he says among other things:
“While enlightenment evokes the certainty of exiting samsara, nirvana is an experience of unconditioned reality, which is therefore more than just the extinction of samsara. In Theravda, the possibility of temporary experiences of nirvana before attaining final enlightenment is mentioned during the practice of jhana meditation. Once awakened, an arhat or a perfect Buddha can enter and leave the nirvana dimension at will. They enter there definitively when they become extinct: it is the parinibbãna. According to the schools and vehicles, we will find different definitions and different types of nirvana.”
I’m having a little trouble understanding, because I thought that once you reach enlightenment (= deep realization of the nature of phenomena), then you automatically reach nirvana (= end of suffering, of illusion). But there, the specialist explains that a Buddha and an arhat can go out of nirvana.
Moreover, I thought that once one has reached nirvana, it necessarily means that one has reached the definitive Awakening. But the scholar says that for Theravada, one can reach nirvana (through the jhânas) without having yet reached final enlightenment.
“Bhikkhus, there are these two Nibbāna-elements. What are the two? The Nibbāna-element with residue left and the Nibbāna-element with no residue left.
“What, bhikkhus, is the Nibbāna-element with residue left? Here a bhikkhu is an arahant, one whose taints are destroyed, the holy life fulfilled, who has done what had to be done, laid down the burden, attained the goal, destroyed the fetters of being, completely released through final knowledge. However, his five sense faculties remain unimpaired, by which he still experiences what is agreeable and disagreeable and feels pleasure and pain. It is the extinction of attachment, hate, and delusion in him that is called the Nibbāna-element with residue left.
“Now what, bhikkhus, is the Nibbāna-element with no residue left? Here a bhikkhu is an arahant … completely released through final knowledge. For him, here in this very life, all that is experienced, not being delighted in, will be extinguished. That, bhikkhus, is called the Nibbāna-element with no residue left.
Iti 44
The idea of nibbana as an existent reality after the cessation of the five aggregates is the Nibbana-element with no residue left. An arahat (an awakened person) is said to be in Nibbana-element with residue left during their lifetime; this state is simply a life devoid of greed, hatred, and delusion, but it isn’t the same as parinibbana (Nibbana-element with no residue left). The latter means that the five aggregates have ceased and won’t arise again.
They mean that the experience of nibbana-element with no residue left can be experienced before parinibbana.
In other words, final enlightenment means arahatship or nibbana with residue left, not nibbana with no residue left; however, the latter could be experienced during the lifetime of an arahat.
“Now this, bhikkhus, is the noble truth of dukkha: birth is dukkha, aging is dukkha, illness is dukkha, death is dukkha; union with what is displeasing is dukkha; separation from what is pleasing is dukkha; not to get what one wants is dukkha; in brief, the five aggregates subject to clinging are dukkha."
SN 56:11
While an arahat is alive, they still suffer (i.e. experience dukkha) because the aggregates are still present. That is, nibbana with no residue left still has suffering.
Some people also claim that nibbana with no residue left isn’t exactly a state. I recommend the following text to clarify this:
