In the First Series of the Essays on the Gita, Sri Aurobindo outlines the major teachings of the Bhagavad Gita as set forth in its broadest form in the first six chapters of the Gita. The remaining 12 chapters of the Gita return to these themes, this time in more specificity and detail as the outline is filled in and the teaching made complete. Along the way, Sri Krishna takes the opportunity to weave in the yoga of devotion more completely than it has been done, and he also describes the concept of the Purushottama which has been hinted at early on, but not fully explicated. There is also perhaps the finest review of the action of the three Gunas, to provide a practical insight into their operation; and in the eleventh chapter, the incredibly powerful vision of the world-spirit granted to Arjuna.
Sri Aurobindo outlines the remaining 12 chapters as we take up the Second Series of his Essays on the Gita: “The seventh to the twelfth chapters lay down a large metaphysical statement of the nature of the Divine Being and on that foundation closely relate and synthetise knowledge and devotion, just as the first part of the Gita related and synthetised works and knowledge.” “Afterwards the Gita proceeds by the differentiation of Purusha and Prakriti to work out its ideas of the action of the Gunas, of the ascension beyond the Gunas and of the culmination of desireless works with knowledge where that coalesces with Bhakti,–knowledge, works and love made one,–and it rises thence to its great finale, the supreme secret of self-surrender to the Master of Existence.”
The Gita is presenting its teachings to a time that had moved away from the purely symbolical and psycho-spiritual ways of knowing that characterize the age of the Vedas and the Upanishads. It thus attempts to render into intellectual terms some sense of that deeper knowledge to satisfy the mind, and turn it toward the spiritual pursuits that bring with them the true fruits of spiritual growth.
“The reason has to be led to a truth beyond itself, but by its own means and in its own manner. Offered a spiritually psychological solution of the data of which it has no experience, it can only be assured of its validity if it is satisfied by an intellectual statement of the truths of being upon which the solution rests.”
Sri Aurobindo, Essays on the Gita, Second Series, Part I, Chapter 1, The Two Natures, pp. 251-252