I've made several references over the last year and a half to the Numata lectures by Professor Richard Gombrich in 2006. These are in the process of being published as a book. I have been re-reading the notes from those lectures and wanted to highlight lecture seven which discussed the use of fire as a metaphor by the Buddha.
Anyone familiar with the discourses of the Buddha will most likely have clocked that the Buddha uses fire as a metaphor in several different ways. Most notably there is the fire sermon (Āditta-pariyāya, Vin i.34-5) in which the Buddha tells the monks that "everything is on fire". What the Buddha means by "everything" is the five sense faculties and the mind, the objects of our senses, and the whole psychological process of experience. What he means by "on fire" is that we our experience is burning with desire, with hatred, and with spiritual ignorance. The goal of the Buddhist path is nibbāna (Sanskrit nirvāṇa) which means quite literally the blowing out of a flame, or ceasing to burn.
This much is consonant with the received tradition. However Prof. Gombrich has investigated other aspects of this fire metaphor. One of the most interesting related to the nidāna chain - the 12 membered list of factors which condition each other and are said to describe the process of repeated becoming in saṃsara. As part of this list we find that desire (taṇhā) gives rise to "clinging" (upādāna), which in turn is what gives rise to becoming (bhavanā). Gombrich suggests that the word upādāna might well have originally been used in it's more concrete sense of "fuel". In this view clinging would be fuel for becoming, and in my opinion this works much better as an explanation of process. Thus the nidāna chain is a continuation of the fire metaphor into the process of dependent arising.
Upādāna is also used in describing the whole of our psycho-physical experience. The khandhas (Sanskrit skandha) are referred to at times as the five aggregates of clinging (pañca-upādāna-kkhandhā). This is an awkward phrase. It makes no more sense, apparently, in Pāli than the translation does in English. Gombrich notes that there is a common Pāli expression for a blazing fire: aggi-khandha. He suggests that upādāna-kkhandha should be read as a contraction of upādāna-aggi-kkhandha and be translated as blazing masses of fuel. The khandas in other words are an extension of the Buddha's use of the fire metaphor. They are the fuel for the burning desire that prolongs our existence.
The Vedic religion was one in which fire played a central role. There is evidence that fire worship goes back well beyond the entry of the Vedic speaking peoples into India. Fire was very much part of the religious imagination of India by the time of the Buddha, and Gombrich argues that it is from this source that the Buddha draws for his fire metaphor. The key evidence here is a difficult paper by Polish academic Joanna Jurewicz which draws parallels between the terms used in the nidāna chain and certain concepts central to the Vedic religion. Professor Jurewicz argues that the Pāli nidāna model can be seen as a polemic against the Vedic cosmogony. The paper is a not easy to follow: ideally one would be well versed in Vedic language and religion as well as Pāli, but it is very interesting, and Professor Gombrich considers the case to have been demonstrated for some kind of influence.
The primary metaphor for consciousness in the Vedic tradition is fire, hence the Buddha framed his understanding of consciousness in similar terms. But whereas the late Vedic tradition contained a notion of absolute consciousness, the Buddha claimed that there is only consciousness of something: like fire consciousness requires fuel to continue, but also crucially despite being a non-random process (i.e. without fuel there can be no fire) fire operates with no guiding "person" behind it.
This is a brief overview of a more technical and thorough discussion by Professor Gombrich. It continues the theme of looking at the way the Buddha drew on the traditions surrounding him, especially the Vedic tradition, of images and concepts with which to communicate his Insight. It also reassesses the way the received tradition explains some technical terms. What Professor Gombrich has shown on more than one occasion is that the received tradition is confused on some points of doctrine or linguistics. This is important for contemporary Buddhists. It emphasises that the Buddhist texts are not divine revelation, they are no infallible and we must be wary of an over literal interpretation of them. In particular where the Buddha used metaphors drawn from the Vedic traditions, there have often be misunderstood by later Buddhists, even in some cases before the canon was written down. Doctrines must be tested against experience.