What Is Time?

We argue that time is the great enabler: it is that which makes causation and change possible. We develop this idea into a functionalist account of time that has some very nice features: (i) it differentiates time from space where needed, (ii) it illuminates time via its connection to causation and change, (iii) it accounts for the apparent multiple realizability of time, and (iv) it correctly classifies worlds that have time as such. We compare our account to three rivals: time as the great necessitator, time as the great informer, and time as the measure of change. We show that treating time as an enabler does better.