Although the compilers of the Pali Canon were not concerned with teaching the physical sciences, there are frequent passages where they cite the behavior of the physical universe, in similes or examples, to illustrate points of doctrine. A number of these passages discuss questions of heat, motion, meteorology, the etiology of diseases, and so forth, in enough detail to show that a common theory underlies their explanation. That theory centers on the concept of 'dhātu,' property or potential. The physical properties presented in this theory are four: those of earth (solidity), liquid, heat, & wind (motion). Three of them — liquid, heat, & wind — are potentially active. When they are aggravated, agitated or provoked — the Pali term here, 'pakuppati', is used also on the psychological level, where it means angered or upset — they act as the underlying cause for activity in nature. Fire, for example, is said to occur when the heat property is provoked.
'There comes a time when the external heat property is provoked and consumes village, town & city, countryside & rural area; and then, coming to the edge of a green district, the edge of a road, the edge of a rocky district, to the water's edge, or to a lush, well-watered area, goes out from lack of sustenance.'
— MN 28
Once a fire has been provoked, it needs 'upādāna' — commonly translated as fuel — to continue burning. Upādāna has other meanings besides fuel, though — one is the nourishment that sustains the life & growth of a tree — and as we will see below, wind can also function as a fire's upādāna. Thus, 'sustenance' would seem to be a more precise translation for the term.
'How do you construe this, young man: Which fire would be more brilliant, luminous, & dazzling — that which burned in dependence on a sustenance of grass & timber, or that which burned in dependence on having relinquished a sustenance of grass & timber?'
'If it were possible, Gotama, for a fire to burn in dependence on having relinquished a sustenance of grass & timber, that fire would be the more brilliant, luminous, & dazzling.'
'It's impossible, young man, there is no way that a fire could burn in dependence on having relinquished a sustenance of grass & timber, aside from a feat of psychic power...'
— MN 99
'Just as a fire, Vaccha, burns with sustenance, and not without sustenance, even so I declare the rebirth of one who has sustenance, and not of one without sustenance.'
'But, Venerable Gotama, at the moment a flame is being swept on by the wind and goes a far distance, what do you say is its sustenance then?'
'Vaccha, when a flame is being swept on by the wind and goes a far distance, I say that it is wind-sustained. The wind, Vaccha, is its sustenance at that time.'
'And at the moment when a being sets this body aside and has not yet attained another body, what do you say is its sustenance then?'
'Actually, Vaccha, when a being sets this body aside and has not yet attained another body, I say that it is craving-sustained. Craving, Vaccha, is its sustenance at that time.'
— SN 44.9
Another meaning for upādāna is clinging, which suggests that, just as a tree clings to the soil that provides its sustenance, fire clings to its fuel. Thus the above passage could also read, 'fire burns with clinging and not without clinging' — a characteristic of fire that was observed in other ancient Asian traditions, such as the Chinese I Ching, as well.
The clinging nature of fire is reflected in a number of other idioms used by the Pali Canon to describe its workings. For one, an object that catches fire is said to get 'stuck' (passive) or to 'stick' (active): Adherence is a two-way process.
'Just as a wing bone or tendon parings, monks, thrown into a fire don't catch fire [lit: 'stick' or 'get stuck'], keep apart, turn aside, and are not drawn in; even so the heart of a monk who spends time often with a mind accustomed to focusing on the repulsive, doesn't stick to the [thought of] engaging in the sexual act, keeps apart, turns aside, and is not drawn in, and remains either indifferent or repelled.'
— AN 7.46
The second side of the attachment — that fire, in sticking to something, gets stuck — is reflected in yet another idiom in the Pali Canon: When it leaves a piece of fuel it has been clinging to, it is said to be released.
'Just as fire... after being released from a house of reeds or a house of grass, burns even gabled houses, plastered, latched, shut against the wind; even so, all dangers that arise, arise from fools, and not from wise people; all disasters... all troubles that arise, arise from fools and not from wise people.'
— MN 115
This sense of fire's being entrapped as it burns echoes the stanza from the Ŝvetāśvatara Upaniṣad, quoted above (page 19), that refers to fire as being 'seized' when ignited by the friction of fire sticks. Apparently the Buddhists were not alone in their time in seeing attachment & entrapment as they watched a fire burn. And this would account for the way early Buddhist poetry tends to couple the image of an extinguished fire with the notion of freedom:
like a flame's going out was the liberation of awareness.
— DN 16
as a flame overthrown by the force of the wind... so the sage freed from mental activity...
— Sn 5.6
So, to summarize: The image of an extinguished fire carried no connotations of annihilation for the early Buddhists. Rather, the aspects of fire that to them had significance for the mind-fire analogy are these: Fire, when burning, is in a state of agitation, dependence, attachment, & entrapment — both clinging & being stuck to its sustenance. Extinguished, it becomes calm, independent, indeterminate, & unattached: It lets go of its sustenance and is released.
This same nexus of events, applied to the workings of the mind, occurs repeatedly in Canonical passages describing the attainment of the goal:
'One attached is unreleased; one unattached is released. Should consciousness, when standing [still], stand attached to form, supported by form [as its object], established on form, watered with delight, it would exhibit growth, increase, & proliferation. Should consciousness, when standing [still], stand attached to feeling... to perception... to fabrications... it would exhibit growth, increase, & proliferation. Were someone to say, "I will describe a coming, a going, a passing away, an arising, a growth, an increase, or a proliferation of consciousness apart from form, from feeling, from perception, from fabrications," that would be impossible.
'If a monk abandons passion for the property of form... feeling... perception... fabrications... consciousness, then owing to the abandoning of passion, the support is cut off, and there is no base for consciousness. Consciousness, thus unestablished, not proliferating, not performing any function, is released. Owing to its release, it stands still. Owing to its stillness, it is contented. Owing to its contentment, it is not agitated. Not agitated, he [the monk] is totally "nibbāna-ed" right within. He discerns that "Birth is ended, the holy life fulfilled, the task done. There is nothing further for this world."'
— SN 22.53
This being the set of events — stillness, independence, unattachment — associated with the extinguishing of a fire and the attainment of the goal, it would appear that of all the etymologies offered to explain the word 'nibbāna,' the one closest to its original connotations is that quoted by Buddhaghosa in The Path of Purification (VIII, 247). There he derives the word from the negative prefix 'nir,' plus 'vāna,' or binding*: 'Unbinding'.
Modern scholars have tended to scorn this derivation as fanciful, and they favor such hypotheses as 'blowing out,' 'not blowing' or 'covering.' But although these hypotheses may make sense in terms of modern Western ideas about fire, they are hardly relevant to the way nibbāna is used in the Canon. Freedom, on the other hand, is more than relevant. It is central, both in the context of ancient Indian theories of fire and in the psychological context of attaining the goal: 'Not agitated, he is totally unbound right within.'
So 'Unbinding' would seem to be the best equivalent for nibbāna we have in English. What kind of unbinding? We have already gained some idea — liberation from dependency & limitations, from agitation & death — but it turns out that nibbāna is not the only term the Buddha borrowed from the workings of fire to describe the workings of the mind. Upādāna is another, and a survey of how he applied it to the mind will help to show what is loosed in the mind's unbinding and how.