analogous to what is meant by “duration,” if duration likewise means something non-existent, some attribute of a living being, a relation, or something similar. For just as spatial extension is said to be a conceptual measure of place, duration is said to be a conceptual measure of time. And just as the mind conceives non-existent spatial regions in relation to the world, as conceptual measures of places, it conceives non-existent stretches of duration before the world, as conceptual measures of times.

This is what some philosophers regard as something actually existent, as is reported of Plato. They relate that he affirms the existence of matter, duration, the void, and the Platonic Forms.