The Bhagavad Gita remains an enigmatic text to many readers. How could the Gita which starts off with the need to preserve dharma call for the complete renouncement of it in its conclusion? It is necessary, in order to answer this question, to delve into the microcosmic origins of this seminal text. For it is the recapitulation in poetic form of the ancient philosopher-scientists’ insights into the mystery of conscious experience.
Abstracting the external universe as simply the world of the sense-objects, these seers focused on the human body, its anatomy as well as function. They inspected carefully the organs of the body and saw them for what they are: mere instruments for a conscious, purely spiritual first principle known as the purusa. This spiritual entity identifies itself so totally with the circuitry of the brain that it has become almost a material sensory-motor entity. This causes purusa to experience births and deaths and afflictions in an endless cycle of existences. The solution then is to educate the purusa regarding his true nature—the ontological category to which he really belongs, which is the same as that of God (the supreme purusa)—and to free him from the dharma of the senses by making him develop a “core consciousness” that is rooted not in matter but in the supreme pure personality.
The ancient seers were not content with sketchy outlines; they wanted to know how exactly purusa experiences the taste of sense objects. Pathways of neural entities stretching from the sensory receptors (vedas) upwards to the cortex of the brain were discovered. However these researches remained exceedingly abstruse to the common man and they felt the need to make it both accessible and interesting. So they introduced into this philosophical and scientific account poetical elements like personification, etc.
There are three chief entities of the microcosm: (a) the spiritual personality (Visnu) of the same essence as God (b) the brain (Brahma) and (c) kaala or time (Siva). Above this trio however stands Krishna (God) poetically conceived as the cowherd, as it were, of the sensory receptors! There has thus been a translocation of God to the neural realm. The import is that he is the supreme innervating entity (paramatma), the supreme actuator of this micro-creation. All those arrayed up against Arjuna, the jiva or purusa connected to the brain, are material personalities while he himself is purely spiritual in nature. The grief that he suffers in this gripping dharmic drama is also, in a sense, the grief of ontological confusion.
These material, neural entities which emanate, from the causative point of view, from the body of the supreme purusa, are categorized into several classes based on property and function (guna, karma; Gita 4.13). To each is assigned a specific dharma. The function of some of them is to acquire knowledge or sense-data; for others, like the controlling nerves (devas) of the ‘sun’ (trachea) and the ‘moon’ (oesophagus) and other structures, it is to do motor-action and to subdue the visceral organs. Some engage specifically in the processing of the sensory products of the ‘cows’ or sensory receptors; while for others the dharma is to aid and serve the other entities.
In such a microcosmic milieu, the ignorant purusa works. He thinks himself to be a ‘man,’ a neural entity, and engages in ‘work’ (karma) as dictated by the vedas or the sensory receptors. Moreover, corresponding to his microcosmic ignorance, there is an equivalent ignorance reflected externally in the realm of praxis. The path of karma then becomes a path of emulation by the material man of essentially two kinds of neuronal activity. In the first mode known as pravritti, alluded to by Krishna (3.14), there is a metaphorical sacrifice, a yajna, going on in the body. Krishna talks about anna sustaining all creatures and this anna, he says, is produced through rain which in turn is made possible by karma performed in yajna. This esoteric passage refers to the purely autonomic loop of neurophysiology that does not involve conscious perception by the spiritual personality; specifically, the homeostatic regulation of inspiration (breathing). Here, the ‘oblations’ of yajna are the transmitted signals; the neural network through which these ascend to the ‘heavens’ (the base of the brain) is the ‘fire,’ and the deva which is ‘propitiated’ in this process is the activated nerve of inspiration. The ‘rain’, of course, is oxygen and from it, respiratory metabolism takes place (‘food’ is produced) and from this ‘food’, the neural entities are further nourished.
But in the second mode, the ‘oblations’ of this internal yajna are offered, as it were, to the spiritual personality (Visnu). In technical terms, this is the ‘somatosensory afferent’ mode where sensations of touch, pressure, heat, etc. are relayed up to purusa for conscious perception through the highest point of the cerebral cortex. This forms the basis of the path of nivritti or niskama karma.
It is clear from these microcosmic origins that the path of karma is purely material. Even in the second variant, the purusa continues to function as a material entity but does karma by offering to the supreme purusa. None of these reflects the true nature and function of purusa. As karma pertains only to the material, non-conscious units and not to conscious personality, its practice can be sustained only in the state of ignorance. The doer of karma—the neuronal man—must be instructed to cultivate knowledge of spirit and sublimate his consciousness. It is for this reason that the entire dialogic strategy of the Gita transitions from the karmic to the bhaktic. To the jiva, it is recurrently told that he is not a neural entity but an amsa (15.7) of the supreme spirit, not ksara but aksara, immutable (15.16), that like the ‘knower of the field’, he is distinct from the mind, body and senses and that for the one taking delight in atman, there is no karma (3.17). The glory of paramatma is brought before him so that his consciousness becomes undeviatingly rooted in spirit.
The great ontological crisis is thus lifted. However, as soon as the purusa comes out of material mode, his previous microcosmic emulations must also go for these dharmas which are rooted in the philosophy of karma are no longer compatible with his reclaimed status of spiritual personality. Therefore the final call-to-action of the Gita is of sole-refuge (eka sarana) in God forsaking completely all veda-ordained dharmas (18.66).
 sarva dharman parityajya mamekam saranam vraja… ‘Forsaking completely all dharmas, O Arjuna, take sole-refuge in me alone. I will liberate you from all sins, do not grieve’. Gita, v.18.66.
 go pade beda indriyaka buli… ‘By the term ‘go’ (cow) is meant the sensory receptors (beda indriya). And, as the Lord preserves these, he is known as ‘Gopala’. Madhavadeva, Nama Ghosa (Namanvaya section), v. 166.
 annad bhavanti bhutani… ‘From food creatures come into being; from rain is the birth of food; from sacrifice rain comes into being and sacrifice is born of work.’ Radhakrishnan, The Bhagavadgita, p. 136.
 “Information from […] sensors is conveyed along nerves to the respiratory centers in the brain stem. […] Feedback control: Receptors play important roles in the regulation of respiration…” https://en.wikipedia.org/wiki/Control_of_ventilation