One indicator that you are touching the background of awareness or of beingness is the dissolution of certain philosophical problems in particular that of solipsism or of 'other minds'. It's not a matter of a solution to this but that the terms in which the problem would most naturally arise no longer apply. This is in a sense the same as being outside of metaphysics. It is very striking, but in the initial stage it remains a limit realisation and is of the same 'size' as the ordinary sense of self, or of what was understood that way. Size however is also a metaphysical notion and is tied to space and time, so you know that this too will go, will yield to something entirely wild.