It is involved in the meaning of this property of 'moving on' that not only is any act of sense-awareness just that act and no other, but the terminus of each act is also unique and is the terminus of no other act.

Sense-awareness seizes its only chance and presents for knowledge something which is for it alone.
There are two senses in which the terminus of sense-awareness is unique.
It is unique for the sense-awareness of an individual mind and it is unique for the sense-awareness of all minds which are operating under natural conditions.

There is an important distinction between the two cases.

(i) For one mind not only is the discerned component of the general fact exhibited in any act of sense-awareness distinct from the discerned component of the general fact exhibited in any other act of sense-awareness of that mind, but the two corresponding durations which are respectively related by simultaneity to the two discerned components are necessarily distinct.

This is an exhibition of the temporal passage of nature; namely, one duration has passed into the other.