Full Idea
Posidonius defined time thus: it is an interval of motion, or the measure of speed and slowness.
Gist of Idea
Time is an interval of motion, or the measure of speed
Source
report of Posidonius (fragments/reports [c.95 BCE]) by John Stobaeus - Anthology 1.08.42
Book Reference
'The Stoics Reader', ed/tr. Inwood,B/Gerson,L.P. [Hackett 2008], p.88
A Reaction
Hm. Can we define motion or speed without alluding to time? Looks like we have to define them as a conjoined pair, which means we cannot fully understand either of them.