Sri Aurobindo, The Life Divine, p.890
It is for that reason Sri Aurobindo says: a further intention is there and this is not yet accomplished, and this is yet to be accomplished. In sadharmya mukti, our whole being becomes entirely divinised. This complete divinisation is called by Sri Aurobindo: transformation: complete divinisation. And this complete divinisation requires three processes: psychic transformation, spiritual transformation, and supramental transformation. These are three processes.
I think we shall read this second paragraph and end today. The last line of the first paragraph is (page 890):
..."the spiritual man has evolved, but not the supramental being who shall thenceforward be the leader of that nature.
“This is because the principle of spirituality has yet to affirm itself in its own complete right and sovereignty; it has been up till now a power for the mental being to escape from itself or to refine and raise itself to a spiritual poise, it has availed for the release of the Spirit from mind and for the enlargement of the being in a spiritualised mind and heart, but not, – or rather not yet sufficiently, – for the self-affirmation of the Spirit in its own dynamic and sovereign mastery free from the mind's limitations and from the mental instrumentation. The development of another instrumentation has begun, but has yet to become total and effective; it has besides to cease to be a purely individual self-creation in an original Ignorance, something supernormal to earth-life that must always be acquired as an individual achievement by a difficult endeavour. It must become the normal nature of a new type of being; as Mind is established here on a basis of Ignorance seeking for Knowledge and growing into Knowledge, so Supermind must be established here on a basis of Knowledge growing into its own greater Light. But this cannot be so long as the spiritual-mental being has not risen fully to Supermind and brought down its powers into terrestrial existence. For the gulf between Mind and Supermind has to be bridged, the closed passages opened and roads of ascent and descent created where there is now a void and a silence. This can be done only by the triple transformation to which we have already made a passing reference: there must first be the psychic change, the conversion of our whole present nature into a soul-instrumentation; on that or along with that there must be the spiritual change, the descent of a higher Light, Knowledge, Power, Force, Bliss, Purity into the whole being, even into the lowest recesses of the life and body, even into the darkness of our subconscience; last, there must supervene the supramental transmutation, – there must take place as the crowning movement the ascent into the Supermind and the transforming descent of the supramental Consciousness into our entire being and nature."
Sri Krishna speaks of para prakriti in the Bhagavad Gita as his higher nature which is the other word for supermind. So the key that is given at the end is the key to bring down the supermind on the earth so that sadharmya-mukti can be attained. The whole chapter actually is a description of how this can be done, the whole process is given, the entire map is given.