ABSTRACT
The rational theory of clocks requires that time be date-indifferent, but not that it be continuous. Time should thus be contrasted with simple angles, which have a natural zero and a natural unit, with temperature, which has a natural zero but no natural unit, and with periodic processes, which have a natural unit but no natural zero. Time is not scale-invariant in the way that geometrical properties are scale-invariant in Euclidean space. The homogeneity of time is not simply a fact forced on us by experience, but, like continuity and date-indifference, also a fiat, something we impose on our schemata for organizing experience. The time required by the rational theory of clocks has certain desirable topological properties, but is very tenuous, and is emptied of all significance and almost all reality.
