We are to consider each, namely both time and space, to be a separate and independent system of entities, each system known to us in itself and for itself concurrently with our knowledge of the events of nature.

Time is the ordered succession of durationless instants; and these instants are known to us merely as the relata in the serial relation which is the time-ordering relation, and the time-ordering relation is merely known to us as relating the instants.

Namely, the relation and the instants are jointly known to us in our apprehension of time, each implying the other.
This is the absolute theory of time.

Frankly, I confess that it seems to me to be very unplausible.

I cannot in my own knowledge find anything corresponding to the bare time of the absolute theory.