Only as a sequence do we appear to exist.
And without succession in time there could not appear to be 'an I'.
The Buddhistic and Vedantic negation of a self (anatta) is automatically realised the moment the concept of seriality disappears.
That is why our phenomenal 'existence' is entirely dependent on the notion of 'time', in the absence of which what we are is necessarily intemporal and non-phenomenal.
