Are the five elements underemphasized in Buddhism?

In Buddhism, the four Great Elements (Pali: cattāro mahābhūtāni) are earth, water, fire and air. Mahābhūta is generally synonymous with catudhātu, which is Pāli for the "Four Elements."[5] In early Buddhism, the Four Elements are a basis for understanding and for liberating oneself from suffering.

Definitions
In the Pali canon,[6] the most basic elements are usually identified as four in number but, on occasion, a fifth and, to an even lesser extent, a sixth element may be also be identified.


Four primary elements
In canonical texts, the four Great Elements refer to elements that are both "external" (that is, outside the body, such as a river) and "internal" (that is, of the body, such as blood). These elements are described as follows:

Earth element (paṭhavī-dhātu)
Internal earth elements include head hair, body hair, nails, teeth, skin, flesh, sinews, bone, organs, intestinal material, etc.[7]
Water (or liquid) element (āpo-dhātu)
Internal water elements include bile, phlegm, pus, blood, sweat, fat, tears, nasal mucus, urine, etc.[8]
Fire element (tejo-dhātu)
Internal fire elements include those bodily mechanisms that produce physical warmth, aging, digestion, etc.
Air (or wind) element (vāyo-dhātu)
Internal air elements includes air associated with the pulmonary system (for example, for breathing), the intestinal system ("winds in the belly and ... bowels"), etc.
These four elements are described as "primary" or "underived" (no-upādā) matter (rūpa), meaning that they cannot be analyzed into further atomistic units. While underived, this does not mean that they are "unconditioned."[9] Thus, for instance, according to the 5th c. CE commentarial Visuddhimagga, "as to the proximate cause, each [element] has the other three as its proximate cause."[10]


Fifth and sixth elements
In addition to the above four elements of underived matter, two other elements are occasionally found in the Pali Canon:[11]

Space element (ākāsa-dhātu)
Internal space elements includes bodily orifices such as the ears, nostrils, mouth, anus, etc.
Consciousness element (viññāṇa-dhātu)
Described as "pure and bright" (parisuddhaṃ pariyodātaṃ), used to cognize the three feelings (vedana) of pleasure, pain and neither-pleasure-nor-pain, and the arising and passing of the sense contact (phassa) upon which these feelings are dependent.
According to the Abhidhamma Pitaka, the "space element" is identified as "secondary" or "derived" (upādā).[12]


Soteriological uses
The Four Elements are used in Buddhist texts to both elucidate the concept of suffering (dukkha) and as an object of meditation. The earliest Buddhist texts explain that the four primary material elements are the sensory qualities solidity, fluidity, temperature, and mobility; their characterization as earth, water, fire, and air, respectively, is declared an abstraction -- instead of concentrating on the fact of material existence, one observes how a physical thing is sensed, felt, perceived.[13]


Understanding suffering
The Four Elements pertinence to the Buddhist notion of suffering comes about due to:

The Four Elements are the primary component of "form" (rūpa).
"Form" is first category of the "Five Aggregates" (khandhas).
The Five Aggregates are the ultimate basis for suffering (dukkha) in the "Four Noble Truths."
Schematically, this can be represented in reverse order as:

Four Noble Truths → Suffering → Aggregates → Form → Four Elements
Thus, to deeply understand the Buddha's Four Noble Truths, it is beneficial to have an understanding of the Great Elements.


Meditation object
In the Mahasatipatthana Sutta ("The Greater Discourse on the Foundations of Mindfulness," DN 22), in listing various bodily meditation techniques, the Buddha instructs:

"...Just as if a skilled butcher or his assistant, having slaughtered a cow, were to sit at a crossroads with the carcass divided into portions, so a monk reviews this very body ... in terms of the elements: 'There are in this body the earth-element, the water-element, the fire-element, the air-element.' So he abides contemplating body as body internally...."[14]
In the Visuddhimagga's well-known list of forty meditation objects (kammaṭṭhāna), the great elements are listed as the first four objects.