I’ve been thinking about time recently. Not the fact that I’m running out of it, or how I’m wasting it, or what to do with it. No. Time itself, or our sense of time. Once you start thinking about time, you come across a real paradox. When I did a little investigating, I discovered that the problem that struck me had actually occurred first to St. Augustine, of all people.

Here it is.

The past has already happened. So it’s gone.

The future hasn’t happened yet, so it doesn’t exist, either (not yet, anyway).

As for the present, it has no duration. If it did, it would necessarily have parts that came earlier and later—it would mean that the present would have its own past. To get a bit technical, the present instant isn’t exactly instantaneous. It is equivalent to what’s called Planck Time. According to quantum physics, this is the shortest interval possible, far too short to be perceptible to human consciousness.

If this is correct, how is it that we have the sense of things happening in the present? We observe the second hand of a clock sweep, watch a glass as it falls. We hear a person talk or a chord of music play. And we seem to experience it all as it happens right now.

That’s the paradox.

I read some time ago in a book by Michael Gazzaniga called The Mind’s Past that our brains receive and process information from various parts of our bodies at different rates. For instance, nerve signals arriving from our feet take a bit longer to reach our brains than nerve signals coming from our eyes. But if you touch your toe, you seem to see it and feel it at the same time. In order to correlate these various sensory inputs, to build up a coherent sense of the external world in our consciousness, our minds have to be slightly time-delayed.

That image coming from our eyes has to be held and stored so that slower-moving sensory data can be correlated with it. Thus sight, sound, and touch all seem to happen to us simultaneously.

But that means that what we experience as the present is actually happening a fraction of a second in the past.

It gets even stranger. I had a Rewire Me moment when I came across the notion of the “specious present,” a term first introduced by the psychologist E. R. Clay around the turn of the twentieth century.

Distinct from past, future, or “real present” (the present that none of us actually experience), it is a mental state that may be related to what neurologists call short-term memory—although it might make more sense to borrow a computer term and call it active memory.

According to this idea of the specious present, all of us spend our lives not in the “real present” but rather in a neurologically created zone of active memory. What we think of as happening now has actually already happened. The sense of “nowness” is an illusion (one of many) that our brains generate in order to help us navigate reality.

Take vision, for example. Light enters our eyes and is projected upside down on the interior of our retinas. Our brains combine these two internal inverted images into a single external three-dimensional image of the outside world.

The visual environment that we experience is not what our eyes see. It is an internal environment that our brains construct in order to help us more effectively navigate the outside world. For similar reasons, our brains have evolved to allow us to experience the environment of time.

It is only by allowing us to hold on to a short piece of the recent past—in essence, to occupy it as if it were an ongoing and persistent present—that we are able to truly have experiences at all.

So the next time someone accuses you of living in the past, don’t worry about it.

We all do.

Read about Neal Marshall Stevens.