This idea (and its paradoxical consequences) will occupy Augustine for the rest of Book XI. He strengthens his proof that time does not exist with a lengthy discussion of past, present and future. Neither past nor future, he points out, actually exist--the past is certainly not extant now, and neither is the future (if they were, they would be the present). Even the present is hard to pin down; Augustine divides it into years, months, days, and so on, eventually determining that the present itself cannot truly be said to exist. The present occupies "no space" of course, but it also has "no duration" (any duration would immediately become past and future, which do not exist). Thus, when we look for time we find it to have no real existence.
Nonetheless, time would seem to have some sort of existence, since we can all talk about it and even measure it. The best Augustine can do here is to say that time can only exist in the present, through the mechanisms of memory and prediction. The past is nothing but memory images that exist in the present. The future, on the other hand, gets its apparent existence from predictions based on signs that exist in the present. With this provisional account of "where" time exists, Augustine is willing to accept the common "usage" of the terms past, present, and future (as long as we know we are actually only referring to a present instant without duration).
Augustine still has a problem, however, because it does appear that we can measure time. Yet how could we possibly be measuring something that has no actual duration and (of course) no extension? A provisional answer may lie in the fact that we seem to measure time as it "passes" through the present moment.
This still leaves us, however, with the paradox of measurement--we may measure time as it passes us, but with what? Given only the present instant, what increments could we possibly use to measure something with no duration or extension?
Augustine toys with and dismisses some possible accounts of temporal measurement put forth by others, most significantly the astronomically inspired idea that time is measured by the movements of the heavenly bodies. He argues strongly that bodies, heavenly or otherwise, move in time, and are not themselves definitive of time. The course of the sun may mark a day, but twenty-four hours would still pass if the sun stopped.
Augustine has now debunked a number of ideas about time, namely the idea that it has any existence other than in a durationless present instant. He still, however, cannot account for the "time" with which we all are familiar. Indeed, he will not provide a solid answer at all. He does make one suggestion, however: time seems to be a sort of "distention" (distentio; stretching) of the soul. The soul, which should be abiding in the eternal present (since no other time truly exists), becomes stretched out into temporality, into an apparent successiveness of events.
This idea, though it goes largely unexplicated, comes from Plotinus, who wrote of time as "a spreading out of life." Unlike Plotinus, however, Augustine sees this stretching or distension as a painful fall away from God. This is another version of the fall from God's eternal, unified, and unchanging grace into the created world of multiplicity and temporality.
Augustine does offer some brief confirmation of this idea that time is a property not of the external world but rather of the soul itself. Returning to the issue of memory, he notes that when we appear to be measuring time as some property of the world, we are actually measuring something in our own memory. Since the past does not truly exist, we can only be considering the images of past times as they are now retained within us. Thus, it would indeed seem that time is some property of the mind (or soul) itself, perhaps a kind of "distention."
Augustine closes this discussion with a comparison between his own existence in temporality and God's existence in eternity. Augustine, muddled in his complex pursuit of the nature of time, finds himself "scattered in times whose order I do not understand." For God, on the other hand, it is not simply a matter of being able to know all times (as a superhuman might), but a matter of the unity of all times in a single, timeless eternity.