Sri Aurobindo, in his magnum opus The Life Divine resolves the contradiction between the way of the ascetic and the creed of the materialist by declaring that the Truth of existence incorporates the ideals sought by each in a unifed whole which he called “Reality Omnipresent”.
There are certain traditions in the Buddhists Tantra, particularly the Mahamudra, Dzogchen, the “great symbol” that recognize that Samsara, the world of multiplicity, the illusory world operating on the principle of desire, and Nirvana, the world of unity and absence of desire, are both present “here”.
The Gita itself integrates the Upanishadic dicta of “One Without a Second” and “All This is the Brahman” by its unwavering focus on the Oneness of all existence. The Gita does not recognize the apparent duality as being ultimately real. Whatever the apparent differences, the Divine Spirit occupies the world, makes up the entire multiplicity of forms and forces while at the same time it is the immobile, the silent, the uninvolved witness of existence. The “two birds” of the Upanishads, one eating the fruit of the tree, the other observing unmoved are ONE existence to the Gita.
Sri Aurobindo describes the Gita’s view: “This utmost undividing Monism sees the one as the one even in the multiplicities of Nature, in all aspects, as much in the reality of self and of cosmos as in that greatest reality of the supracosmic which is the source of self and the truth of the cosmos and is not bound either by any affirmation of universal becoming or by any universal or absolute negation.”
For the Gita, this is not a truth of philosophy, but a truth to be lived, experienced and understood with all the faculties. The truth is not something of the mind, but of the being. “Absolutely to know it, to seize it in knowledge and feeling and force and experience is to be perfected in the transformed understanding, divinely satisfied in heart and successful in the supreme sense and objective of all will and action and works. It is the way to be immortal to rise towards the highest divine nature and to assume the eternal Dharma.”
Sri Aurobindo, Essays on the Gita, Second Series, Part II, Chapter 15, The Three Purushas, pg. 434