With everything that Arjuna has learned, seen and experienced in the teaching thus far, he still must address the conventional knowledge of his time and reorient his process of understanding. It is as if everyone believed that the world was flat, until one day an intrepid explorer circumnavigated the globe and reported that it is round. The whole consciousness must needs address the radical change and build a new framework for the understanding that develops.
Similarly, the wisdom of his time indicated that true wisdom and liberation must be obtained by abandoning the illusory goals and rewards set before one in worldly action; that the true divine status was silent, immutable and eternal, not troubled by anything that might occur in the world.
Sri Krishna has now shown Arjuna that, while he must start by freeing himself from attachment and desire that bound him to the ordinary life, the true liberation would actually come when he could integrate the immutable and the mutable in the larger frame of the Purushottama, and that a life of dedicated action and devotion was actually going to lead him to a higher realisation than the traditional yoga of knowledge of his time would indicate.
Sri Aurobindo highlights Arjuna’s quandary: “Those devotees who thus by a constant union seek after thee, tvam, and those who seek after the unmanifest Immutable, which of these have the greater knowledge of Yoga?”
The issue is “This eternal Self is the greater Principle according to all current notions and the Godhead in the manifestation is an inferior figure: the unmanifest and not the manifest is the eternal Spirit. How then does the union which admits the manifestation, admits the lesser thing, come yet to be the greater Yoga-knowledge?”
Sri Aurobindo, Essays on the Gita, Second Series, Part I, Chapter 12, The Way and the Bhakta, pp. 384-385