Concept of ultimate reality in Bhagavad Gita is defined, as in the Upanishads, by two ways of analysis, first of the objective and second of the subjective. Bhagavad Gita does not provide any arguments in support of the metaphysical position. Further, Upanishads confirm the reality of Supreme Brahman one without determinations or attributes. The objective analysis proceeds on the basis of a distinction between substance and shadow, the immortal and the perishable, the aksara and the ksara. There are these two beings in the world, the destructible ksara and the indestructible aksara.

Bhagavad Gita declares that the Supreme Being is called the highest self, Paramatman. The author of Gita first distinguishes the permanent background of the world from its transitory manifestations, the Prakirti from its changes. This supreme spirit is the true immortal, the abode of the eternal. It is also quite possible to interpret the conception of Purusottama as that of the concrete personality which is superior to the false abstractions of the infinite and the finite. The only difficulty is that Brahman, declared to be the basis of the finite, cannot be looked upon as a mere abstraction. Bhagavad Gita distinguishes between the finite or the impermanent, and the infinite or the permanent. Whatever is limited or transitory is not real. All becoming is an untenable contradiction.

Since the things of the world are struggling to become something else, they are not real. The individual self is ever unsatisfied with it and is struggling always to become something else. In its consciousness of limitation, there is a sense of the infinite. The empirical mind is ever changing. About the nature of the supreme self, the account presented in Bhagavad Gita is rather puzzling. The individual form may change, but the essence is not destroyed. Until perfection is obtained, individuality persists. However repeatedly the mortal frame is destroyed, the inner individuality preserves its identity and takes on a new form. It is by this affirmation of the soul, by this justification of the intuition of the Upanishads, that the Atman, or the pure subject, remains unaffected.

In the spirit of the Upanishads Gita identifies the two principles of the Atman and the Brahman. Behind the fleeting senses and the body there is the Atman; behind the fleeting objects of the world there is Brahman. The two are one, being of identical nature. Any endeavour to define the unchanging in terms of the changing fails. There is, however, no attempt in the Gita to prove that the absolute discerned by intuition is the logical foundation of the world, though this is implied. Bhagavad Gita asserts the truth of an advaita or non-dualism in philosophy. The supreme Brahman is considered as the immutable self-existence, to which the doers of the austerities attain. It is the highest status and supreme goal of the soul`s movement in time, though it is itself no movement, but a status original, eternal and supreme. In the unalterable eternity of Brahman, all that moves and evolves is founded. The two, Brahman and the world, seem to be opposed in features.

The metaphysical idealism of the Upanishads is transformed in the Gita into a theistic religion, providing room for love, faith, prayer and devotion. The supreme soul is the origin and cause of the world, the indivisible energy pervading all life. Moral attributes are combined with the metaphysical. The supreme is said to be possessed of two natures higher, para, and lower, apara, answering to the conscious and the unconscious aspects of the universe. The lower prakriti produces effects and modifications in the world of nature or of causes; the higher prakriti gives rise to intelligent souls, in the world of ends or values. While dwelling in man and nature the Supreme is greater than both.

The theory of avatars brings to mankind a new spiritual message. The avatars are the militant gods struggling against sin and evil, death and destruction. An avatar is a descent of God into man, and not an ascent of man into God. Though every conscious being is such a descent, it is only a veiled manifestation. The philosophical intellect tries to relate the avatars, or the ideals of perfection, to the great onward march of the world. On ultimate analysis the assumption of the form of Purusottama by the absolute becomes less than real. It is therefore wrong to argue that according to the Gita the impersonal self is lower in reality than the personal Ishvara, though it is true that the Gita considers the conception of a personal God to be more useful for religious purposes.