BG Chap 8 - Brahman and Adhyatma
In this chapter entitled "Taraka Brahma yoga" (Yoga of Brahman realization), Kṛṣṇa will explain the different items starting with Brahman mentioned at the end of the last chapter. He also speaks about pure bhakti and yoga-miśra-bhakti (bhakti mixed with yoga) and the destination of the yogīs.
Brahma refers to the indestructible jīvātmā, whose constitution never changes. The śruti confirms that the jīva is called Brahman when it says: Avyakta (subtle state of prakṛti) merges into akṣara (aggregate of the jīvas); akṣara merges into tamas and tamas merges into the Lord. Akṣara here cannot refer to the Lord since it merges into tamas, which merges into the Lord. Beyond Brahman, however, is Para Brahman, the Lord.
Adhyātma refers to the svabhāva, which produces one’s self from imposition of a body. Thus it means the jīva, since it creates the body. Or the meaning of svabhāva can be that which causes one to attain the Paramātmā. In this case adhyātma refers to the purified jīva. Baladeva Vidyābhūṣaṇa says adhyātma refers to the impressions held in subtle elements which accompany the jīva birth after birth. Thus adhyātma refers to the nature of the jīva. The constitutional position of the jīva is to serve the Lord but in material consciousness his nature is to be the lord of matter.