Sravana I'd always thought was the hearing of a mahavakya for the first time and getting it to such an extent that enlightenment ensued. What else could make sense for if there were a time lag then the spontaneous generation of knowledge would not have occured. The natural question to ask was whether anyone had achieved this sort of immediate enlightenment. No one could tell me. I drew a sort of hand waving assertion that it was possible provided that the person were prepared enough. I took it to be a logical theoretical possibility if the status of sabda pramana were to be maintained.
I was prepared to leave it at that until I read Anantanand Rambachan's doctoral thesis on the common error amongst modern vedantins of placing the anubhava wrought by nidhidhyasana as central to enlightenment.
It is virtually assumed that without some sort of samadhi there can be no enlightenment. This is the confirming event of what was first told to the seeker in the form of the mahavakya. 'Hold it', says A.R. 'sabda pramana is freestanding and does not require confirmation by any other pramana'. No pramana requires another pramanas confirmation.
We nod and think we are for another spin on the carousel. However in the middle of the revolution there is a reversal of spin, a quantum change in which the dead cat comes to life and scratches the leg of a good chair. Yes, the mahavakya is heard as a web of words like wallpaper on the void. This is the initial and only pramana required but it must be dwelt on, manana, and contemplated, nidhidhyasana, for its full purport to be gleaned. The ultimate anubhava should there be one in that case feeds back to the initial pramana, indeed only pramana in this case, the sravana of sabda pramana. Now if you like, and this is my mystic gloss, because time is vanquished, trikalaabheda, in enlightenment we achieve simultaneity with the hearing of the mahavakya. Neat, eh.
Mahavakyas like “tat tvam asi” are carefully analysed to show that the identity imparted is at the level of Awareness alone. Sravana, therefore, incorporates the entire process of Vedantic instruction and encompasses all the traditional methods (e.g. adhyaropa-apavada, neti, neti) employed by the teacher in gradually unfolding brahman.(from pg. 189ff. op.cit.)
Is A.R. in effect saying that there is no confirming experience for enlightenment and that experience as such could not confirm it. Sankara has written as much in his commentary on the Brahma Sutras. More anon.