The First Way shows that the study of nature will never explain actual motion but will only be able, at best, to co-ordinate motions to a more fundamental thing whose actual motion is given. We therefore don’t get an explanation of motion in physics, only facts related to more basic facts.

But if this is true of motion it seems to be also true of time – we never get an explanation of actual time but just a co-ordination of one clock to another. The clock, like motion, becomes a horizon, or a thing that limits experience in a way that we can never transcend by the advance of experience. But, for whatever reason, it feels more profound to notice time as a horizon than to notice that exactly the same thing is true about motion.

Taken like this, eternity related to time like the First Mover relates to motion in our experience – eternity thus explains why we can have an actual time as opposed to just a co-ordination and hierarchy of clocks, each which take time as given. This might also provide analogies to clarify facts about the First Mover too: God is not a First Mover in the sense of being the last mover in a physical analysis any more than he is the one clock we set all of our clocks to.

So perhaps there might be some theology to be done in seeing eternity as an “untimed clock” where “clock” means “any measure that a clock in experience is related to by way of explanation”, though it is “untimed” or impossible, even in principle or the imagination, to be related to some other measure. We can neither measure the duration of the untimed clock by events in nature nor by imagining some more encompassing clock of which its measure is a part. The Untimed Clock therefore encompasses time while not being divisible into it.

Because the Untimed Clock is not divisible into time, there will always be a temptation to understand it through the metaphor of “simultaneity”, or as existing at a point while time exists as a line. This explains its indivisibility very well, but it obviously completely occludes the sense in which it also encompasses or contains time. The metaphor of an irrational quantity might work well as a supplement: we can find no common measure for the circumference and the diameter, though the circumference contains the diameter. A better metaphor would be an instance of asymmetrical measure, where A measured B in whole or part but B didn’t measure A, but this is impossible in Euclidean quantities.