Full Idea
Space and time taken together constitute the order of possibilities of the one entire universe, so that these orders relate not only to what actually is, but also to anything that could be put in its place.
Gist of Idea
Space and time are the order of all possibilities, and don't just relate to what is actual
Source
Gottfried Leibniz (Reply to 'Rorarius' 2nd ed [1702], GP iv 568), quoted by Richard T.W. Arthur - Leibniz 7 'Space and Time'
Book Reference
Arthur, Richard T.W.: 'Leibniz' [Polity 2014], p.153
A Reaction
A very nice idea. Rather like the 'space of reasons', where all rational thought must exist, space and time are the 'space of existence and action'. Their concepts involve more than relations between what actually exists.