'The present has no extension but intensity'. (Lama Anagarika Govinda.)
The present has no duration. Therefore it does not exist in the lineal dimension of time. It is not 'horizontal'. It has only a point of contact with seriality
The extension of the present is in another dimension to that of time. It is therefore at right-angles to time. The direction of measurement of this essentially timeless dimension is - within.
That is the reason of the importance instinctively given to momentaneite, to 'presence in the present', to 'spontaneity', and the reason of the creation of expressions such as 'the Eternal Present'.
The so-called present is our link with the dimension that includes the three we already know and use. It is the point at which Time cuts across Space, and as a concept it is spatial rather than temporal.
The present is not a fleeting moment: it is the only eternity. In Time 'lies' samsara: in the Present 'lies' nirvana. Time is the measurement of objectivity: the Present is the presence of subjectivity, in which everything potentially is, and from which, in Time, everything is apparently projected.
The assumed (so-called) present is our point of contact with bodhi-mind. It is the invisible portal through which intuition reaches us from the interior of ourselves, from that universal and limitless interior (spatially thought-of) which is all we ever were or ever will be, and which is out of time. It is the sole line of communication between our enveloping totality and our apparent existence as separate individual creatures, between our universality and our illusory particularity, between the noumenality and the phenomenality of all sentient beings.
The present alone in our experience is what IS, and phenomenally it is not; for it is only an imaginary division between past and future - like the equator between the northern and southern hemispheres. It is like a fictional line of latitude that is a symbol rather than an existence, and yet represents a vital transmission from one sphere to another, from north to south, from past to future, neither of which has any reality in itself but each of which is a concept that artificially divides a continuity in space or in time.
The present alone represents that which we are in an apparent world in which we are not, since therein we are appearances (phenomena) only. We ourselves neither exist nor do we not exist. Neither existing samsarically nor not-existing nirvanically, we are nothing - in any way in which we can know ourselves - but as the Present.
Note: The present is the dimension I have indicated by the image of 'vertical' being or seeing, which is an essential discrimination for comprehending in what manner we (sentient beings) can be understood to BE. It is also the dimension in which occurs whatever actuality there may be in the expression 'living in Zen', and in 'when I am hungry, I eat; when I am weary, I sleep' - in the manner in which the awakened Masters themselves did that.