Series 1, Chapter 23 pg 237, Para 1: “Sages win Nirvana in the Brahman, they in whom the stains of sin are effaced and the knot of doubt is cut asunder, masters of their selves, who are occupied in doing good to all creatures, sarvabhuta-hite ratah.” That would almost seem to mean that to be thus is to be in Nirvana. But the next verse is quite clear and decisive, “Yatis (those who practise self-mastery by Yoga and austerity) who are delivered from desire and wrath and have gained self-mastery, for them Nirvana in the Brahman exists all about them, encompasses them, they already live in it because they have knowledge of the Self.” That is to say, to have knowledge and possession of the self is to exist in Nirvana. This is clearly a large extension of the idea of Nirvana. Freedom from all stain of the passions, the self-mastery of the equal mind on which that freedom is founded, equality to all beings, sarvabhutesu, and beneficial love for all, final destruction of that doubt and obscurity of the ignorance which keeps us divided from the all-unifying Divine and the knowledge of the One Self within us and in all are evidently the conditions of Nirvana which are laid down in these verses of the Gita, go to constitute it and are its spiritual substance.