Sri Aurobindo
Letters of Sri Aurobindo
CWSA 35
Tibetan Yoga [5]
It would seem that such a reconciliation would be impossible unless someone had overpassed Nirvana or seen something of 
the Higher Evolution or Higher Nature. Perhaps the author had some sort of insight, otherwise he could not state that Nirvana is a spiritual rest-house and that there is a Higher Evolution. For he writes: “The Great Ones and the Bodhisattvas... renounce their right to pass on to a still Higher Evolution and remain within the Cosmos for the good of all sentient beings. It is these Bodhic Forces, thus active in the Cosmos, which... lead mankind, step by step, towards a perfected social order on Earth” [p. 149]. This indicates that they come down or back from Nirvana to lead mankind up to Nirvana. Perhaps it would have been better if they had seen something of the Higher Evolution and then come back to perfect society on earth.
The phrase “to pass on” shows that what is meant by them is an evolution not on earth but somewhere beyond, God knows where. In that case Nirvana would be a place or world on the way to other worlds and the soul evolves from one world to another – e.g. from earth to Nirvana and from Nirvana to some Beyond-Nirvana. This is an entirely European idea and it is most unlikely that it was held by the Buddhists. The Indian idea was that the evolution is here and even the Gods if they want to go beyond their Godhead and get liberation have to come down on earth for the purpose. It is the Western spiritualists and others who think that the birth on earth is a stage of progress from some place inferior to earth and after once being born on earth one does not return but goes to some other world and remains there till one can progress to some other better world and so on and on and on and up and up and up as Ramsay MacDonald would say. Again, this “perfected social order on Earth” is certainly not a Buddhist idea, the Buddhas never dreamed of it – their preoccupation was with helping men towards Nirvana, not towards a perfected order here. All that is a sheer contradiction of Buddhism and smells Europe from 3 miles off.
Current publication:
[Largest or earliest found passage: ] Sri Aurobindo. Letters on Himself and the Ashram // CWSA.- Volume 35. (≈ 26 vol. of SABCL).- Pondicherry: Sri Aurobindo Ashram, 2011.- 658 p.
Other publications:
Sri Aurobindo. Letters on Yoga // SABCL.- Volume 22. (≈ 28 vol. of CWSA).- Pondicherry: Sri Aurobindo Ashram, 1971.- 502 p.