Passing-time is not different from duration, and duration is not different from eternity.
Passing denotes change: something changes. If there is no change no time has passed - which is immutability - for change is movement in space, and time is a measure of movement. Yet immutability, in order to be such, must endure in time.
Immutability, therefore, being absence of movement, is absence of change, absence of passing-time; and so it is duration. But duration 'lasts', and so is subjected to passing-time.
Absence of change - immutability - is conceivable: absence of duration is not, for existence requires duration in order to exist, and duration requires existence in order to endure, so that the absence of the one requires the absence of the other. Duration and existence, therefore, are inseparable: if there is one there must be the other, they are aspects of one another, for without existence there can be no duration, and without duration no existence: they are dual aspects of samsara.
Absence of time, on the other hand, is incompatible with existence, and absence of existence is incompatible with time. Time, therefore, is seen as an aspect of phenomenality, and absence of time is an aspect of noumenality.
There can be no doubt whatever that what-we-are is a phenomenal absence, absence of time and of space, and to the presence of that absence, no name could ever be given, for any name, being a positive noun, must thereby return it to phenomenal presence which would leave it extended in space and in time.
Duration and non-duration cannot be different, for they must be two aspects of whatever they represent. Lasting is sequential in manifestation, and non-lasting is phenomenally non-existing, i.e. not enduring in sequential manifestation.
Non-duration, therefore, is the noumenal form of positive duration, that is to say its negative form which could never be perceived or conceived as a positive concept. It can only be referred to as isness, suchness, or just 'I'.
Timelessness is then seen as the noumenal aspect of Duration, and duration as the phenomenal aspect of it.
