Nibbana (Pali), nirvana (Sanskrit), is the highest spiritual state and the ultimate goal of Buddhism.
The word nibbana comes from nir meaning ‘stop’ and và meaning ‘to blow.’ Thus Nibbana is the extinguishing or blowing out of the fires of greed, hatred and ignorance. Alternatively, it may come from nir plus vana meaning ‘desire’ and thus mean the ‘stopping of desire.’ When, as a result of practicing The Noble Eightfold Middle Path, ignorance and craving give way to knowledge and fulfilment, one attains Nibbana and at death is no longer subject to rebirth and all the suffering that entails.
(from Samyutta Nikaya 43)
Is Nibbana (Nirvana) a physical place? Is it existence? Is it non-existence? These are questions that have been asked by Dhamma / Dharma practitioners and answered in varying ways by Dhamma / Dharma teachers from the time of Buddha through today. The Buddha said:
Everything exists: That is one extreme. Everything doesn't exist: That is a second extreme. Avoiding these two extremes, the Tathagata teaches the Dhamma via the middle: From ignorance as a requisite condition come fabrications . . . (continues with Dependent Orgination formula). (Samyutta Nikaya 12.15)
The Buddha answers no to the following 4 questions / possibilities (Majjhima Nikaya 72 also in Samyutta Nikaya 44.11):
The Buddha is apparently deliberately being vague since no terms in conventional language can do it justice to describe Nibbana. In other Suttas the Buddha argues against nihilism which suggests that Nibbana is not nihilistic. A number of potential explanations have been provided by Buddhist teachers.
A number of teachers have argued that the person does not exist, the being, no matter how great, including the Buddha, cannot be contacted. They argue that there is no soul, no permanent self and that Nibbana is the extinguishment of all defilements, all craving, all suffering, all becoming. They argue that it is not annihilation since there was no being, no soul to begin with.
In the discourse on the 62 kinds of wrong view (Digha Nikaya 1), the Buddha called the following one of the wrong views:
Herein, bhikkhus, recluse or a certain brahmin is a rationalist, an investigator. He declares his view hammered out by reason, deduced from his investigations, following his own flight of thought thus: 'That which is called “the eye,” “the ear,” “the nose,” “the tongue,” and “the body” that self is impermanent, unstable, non-eternal, subject to change. But that which is called “mind” (citta) or “mentality” (mano) or “consciousness” (viññāṇa) that self is permanent, stable, eternal, not subject to change, and it will remain the same just like eternity itself.
The above passage provides support for the view that the one who attains Nibbana, has put down the burden, has completed the task, the aggregates are no more, there is no more false sense of a being and not annihilation since there was no self to begin with.
Other teachers have argued, including Thanissaro Bhikkhu that the being or Mind (Pali: Citta) entering the state of Nibbana is like a “fire unbound.” In the Sutta quoted above, the Buddha talks about a fire that goes out and asks “where did it go” and then refers to the idea that the fire did not disappear, just that it is no longer held by its fuel. Thanissaro Bhikkhu argues that it is like a fire no longer dependent upon the fuel (of a body or the 5 aggregates). In regard to the no self (Anatta) doctrine, Thanissaro Bhikkhu states: “In fact, the one place where the Buddha was asked point-blank whether or not there was a self, he refused to answer.”
Some of the teachers and lay people who hold this type of view do not refer to it as pantheism, but it does have similarities to notions of pantheism found in other Dharmic paths including Hinduism, Jainism, and Sikhism. In the case of Thanissaro Bhikkhu it is clearly not pantheistic as he notes in his No self or not self article: “If one identifies with all of nature, one is pained by every felled tree. It also holds for an entirely “other” universe, in which the sense of alienation and futility would become so debilitating as to make the quest for happiness; one's own or that of others; impossible.” However, although not pantheistic, in the description given to a fire unbound, and reference to a not self concept instead of no self; there is the implication of some kind of subtle existence in Thanissaro Bhikkhu's teachings and also in other teachers of the Thai forest tradition and others in Theravada.
Pantheists sometimes describe the union with the divine as a drop (the mind) entering the divine ocean, no longer existing in an individual sense but still existing in some way. Those holding this view in Buddhism have the following additional quote to support that view: “Just as the river Ganges inclines toward the sea, flows towards the sea, and merges with the sea, so too Master Gotama's assembly with its homeless ones and its householders inclines toward Nibbana, and merges with Nibbana.” (Majjhima Nikaya 73.14)
Note the passage above from the Buddha, that exist or doesn't exist doesn't apply, that he teaches “the Dhamma via the middle.” Can this middle be a subtle existence in a pantheistic way, not as an individual existence but as some form of universal consciousness / the divine? We cannot know for sure without glimpsing Nibbana for ourselves. There is a Mahayana Buddhist passage/riddle that goes: How do you stop a drop of water from drying up? Answer: By placing it in the sea.
The somewhat famous Pabhassara Sutta in the Anguttara Nikaya (1.49 to 1.52) refers to a “luminous mind” (bright or shiny) which has been referenced as referring to Buddha-nature by Mahayana Buddhists and also to a pure mind (not defiled; a “true self”) by some Theravada Buddhists. The Buddha stated: “Luminous, monks, is the mind. And it is freed from incoming defilements.” Pantheists sometimes refer to the mind as a “spark (or shiny element, aspect) of the divine.”
It has been pointed out by some that the Seventh jhana (third formless realm) refers to the sphere of nothingness. If Nibbana is nothingness or simply oblivion, then that would make the Seventh jhana the goal and Nibbana nothing more than the Seventh jhana. But the Buddha attained the seventh and eighth jhanas while still an ascetic, but knew there was more work to be done and later attained full enlightenment, practicing the Middle Way. (See also the link under references for extensive discussion of this at Dhamma Wheel).
Regarding the nature of Nibbana, the question is often asked: Does Nibbana signify only extinction of the defilements and liberation from samsara or does it signify some reality existing in itself? Nibbana is not only the destruction of defilements and the end of samsara but a reality transcendent to the entire world of mundane experience, a reality transcendent to all the realms of phenomenal existence.
The Buddha refers to Nibbana as a 'dhamma'. For example, he says “of all dhammas, conditioned or unconditioned, the most excellent dhamma, the supreme dhamma is, Nibbana”. 'Dhamma' signifies actual realities, the existing realities as opposed to conceptual things. Dhammas are of two types, conditioned and unconditioned. A conditioned dhamma is an actuality which has come into being through causes or conditions, something which arises through the workings of various conditions. The conditioned dhammas are the five aggregates: material form, feeling, perception, mental formations and consciousness. The conditioned dhammas, do not remain static. They go through a ceaseless process of becoming. They arise, undergo transformation and fall away due to its conditionality.
However, the unconditioned dhamma is not produced by causes and conditions. It has the opposite characteristics from the conditioned: it has no arising, no falling away and it undergoes no transformation. Nevertheless, it is an actuality, and the Buddha refers to Nibbana as an unconditioned Dhamma.
The Buddha also refers to Nibbana as an 'ayatana'. This means realm, plane or sphere. It is a sphere where there is nothing at all that correspond to our mundane experience, and therefore it has to be described by way of negations as the negation of all the limited and determinate qualities of conditioned things.
The Buddha also refers to Nibbana as a, 'Dhatu' an element, the 'deathless element'. He compares the element of Nibbana to an ocean. He says that just as the great ocean remains at the same level no matter how much water pours into it from the rivers, without increase or decrease, so the Nibbana element remains the same, no matter whether many or few people attain Nibbana.
He also speaks of Nibbana as something that can be experienced by the body, an experience that is so vivid, so powerful, that it can be described as “touching the deathless element with one's own body.”
The Buddha also refers to Nibbana as a 'state' ('pada') as 'amatapada' - the deathless state - or accutapada, the imperishable state.
Another word used by the Buddha to refer to Nibbana is 'Sacca', which means 'truth', an existing reality. This refers to Nibbana as the truth, a reality that the Noble ones have known through direct experience.
So all these terms, considered as a whole, clearly establish that Nibbana is an actual reality and not the mere destruction of defilements or the cessation of existence. Nibbana is unconditioned, without any origination and is timeless.
Viññanam Anidassanam translates as consciousness without surface, without feature. Some have suggested that this implies there is a sort of consciousness in Nibbana that is not conditioned and beyond the 5 aggregates. This term is found in the Digha Nikaya, Majjhima Nikaya, and Samyutta Nikaya. “Good sir, if that is not partaken of by the allness of all, may it not turn out to be vacuous and empty for you!”
25. “Consciousness non-manifesting, Boundless, luminous all-round.” (Majjhima Nikaya 49)
Others still take it even further, for example the famous Ajahn Mun, who stated that the Buddha even talked to him during his deep meditation experiences, suggesting that the Buddha is at some place in a Buddha-land or Buddha-field. A sizable number of Thai Theravada Buddhists believe that Ajahn Mun and his Dhamma successor, Ajahn Boowa, were fully enlightened arahants. This view is also similar to notions found in other Dharmic paths and also in Mahayana Buddhism.
In the discourse on the 62 kinds of wrong view (Digha Nikaya 1), the Buddha called the following one of the wrong views:
Herein, bhikkhus, a certain recluse or a brahmin asserts the following doctrine and view: 'The self, good sir, has material form; it is composed of the four primary elements and originates from father and mother. Since this self, good sir, is annihilated and destroyed with the breakup of the body and does not exist after death, at this point the self is completely annihilated.' In this way some proclaim the annihilation, destruction, and extermination of an existent being.
The above passage provides support for the view that Nibbana is not annihilation, that there may be some sort of existence or realm.
Nan Huaijin, a major figure in modern Chinese Buddhism and Chán, has criticized what he views as modern nihilistic interpretations of the doctrine of anatta. He has stated that these interpretations are “totally wrong”, and likens them to philosophical materialism. When discussing the Ten Forms of Mindfulness in the Āgamas, he mentions these interpretations of anatta:
“When the Hīnayāna speaks of no self, it is in reference to the manifest forms of presently existing life; the intent is to alert people to transcend this level, and attain Nirvāṇa. But when this flowed into the world of learning, especially when it was disseminated in the West, some people thought that the Buddhist idea of no self was nihilism and that it denied the soul, and they maintained that Buddhism is atheistic. This is really a joke.” [sic]
Over the past several decades (dating back to at least 1939), a controversial movement of monks and meditation masters within Theravada, later called the Dhammakaya Movement, has developed in Thailand. The Dhammakaya Movement teaches that it is incorrect to label Nirvana as anatta (non-Self); instead, Nirvana is claimed to be the ‘True Self’. This teaching is strikingly similar to that of the tathagatagarbha sutras of the Mahayana.
The Madhyamaka school of Nagarjuna includes the Mūlamadhyamakakārikā text which includes:
To say “it is” is to grasp for permanence. To say “it is not” is to adopt the view of nihilism. Therefore a wise person does not say “exists” or “does not exist.” (Mūlamadhyamakakārikā 15.10)
Nagarjuna attempts to explain how the answer does not lie in any of the four possibilities listed above. The language we use frames our conventional reality. Beneath that there is an ultimate reality, such as the condition of the enlightened dead person. One can experience this directly in certain meditative states, but one cannot describe it. To say anything about it would merely succeed in making it part of our conventional reality; it is, therefore, ineffable. In particular, one cannot describe it by using any of the four possibilities furnished by the catuskoti (four possibilities). (Graham Priest, 2014)
Nagarjuna's ineffable position may have support from the Pali Canon too. A potentially fifth alternative to the standard four explanations of exist, non-existence, both, neither; is: inexpressible (which may also fit with some of the subtle forms of existence views shown above). From the Digha Nikaya, Maha Nidana Sutta:
If anyone were to say with regard to a monk whose mind is thus released that 'The Tathagata exists after death,' is his view, that would be mistaken; that 'The Tathagata does not exist after death' that would be mistaken; 'The Tathagata both exists and does not exist after death' that would be mistaken; 'The Tathagata neither exists nor does not exist after death' is his view, that would be mistaken. Why? Having directly known the extent of designation and the extent of the objects of designation, the extent of expression and the extent of the objects of expression, the extent of description and the extent of the objects of description, the extent of discernment and the extent of the objects of discernment, the extent to which the cycle revolves: Having directly known that, the monk is released. [To say that,] 'The monk released, having directly known that, does not see, does not know is his opinion,' that would be mistaken.
Those who hold the classical or orthodox view of Theravada Buddhism have countered that the Samyutta Nikaya refers to teaching via the middle but ends with the regular talk of the cessation of all suffering: “Avoiding both extremes the Tathaagata teaches a doctrine of the middle: Conditioned by ignorance are the formations… [as SN 12.10]… So there comes about the arising of this entire mass of suffering. But from the complete fading away and cessation of ignorance there comes the cessation of the formations, from the cessation of the formations comes the cessation of consciousness… So there comes about the complete cessation of this entire mass of suffering.”
In no place in the Suttas does the Buddha specifically endorse any of the above subtle existence proposals. It is true that the discussion appears vague, but in no way does he say there is any remainder of any of the aggregates including the mind or consciousness. In the Mahaparinibbana Sutta (Digha Nikaya 16) he refers to the Dhamma being the teacher when he is gone, implying that he cannot be contacted (and therefore cannot be in some Buddha-field or realm).
The Theravada commentaries, written from around the 1st century to the 12 century lean toward the view of Bhikkhu Bodhi above and to other views which suggest that it is not non-existence. From the Visudhimagga:
Again, it should not be said that Nibbána does not exist. Why not? Because it then follows that the way would be futile.  For if Nibbána were non- existent, then it would follow that the right way, which includes the three aggregates beginning with virtue and is headed by right understanding, would be futile. And it is not futile because it does reach Nibbána. (Visudhimagga, Ch. XVI)
[non-existence] That is not so. Because it would then follow that the noble path was meaningless. For if it were so, then, since defilements [can be] non-existent also before the moment of the noble path, it follows that the noble path would be meaningless. Consequently that is no reason; [it is unreasonable to say that Nibbána is unapprehendable, that it is non-existence, and so on]. (Visudhimagga, Ch. XVI)
The correct view will be found in the practice when one reaches full enlightenment and experiences Nibbana first hand. Until then Buddhists can continue on with their practice, continuing to follow the teachings and practice as outlined in the Pali Canon and see on their own which one is right or mostly right.