I work all afternoon, completely absorbed, on a paper. After some hours, I sit up and think, “It must be five o’clock already.” I look at my watch: I am right. I feel as if I’ve been sitting here for three hours, and I have been. This sort of feeling is not terribly reliable—how often have you had such a thought, only to find that it is four, or seven?—but usually we give it at least some credence. What sort of feeling is it? It seems to be a perception of an interval of time past? But how could it be?
Let’s put a closely related, but distinct, problem to the side. William James said: “A succession of feelings is not, in and of itself, a feeling of succession.” This puts in question how (for instance) a sequence of heard notes, for example C, E, G, could together constitute a perception of three notes in sequence, C-E-G—the C major progression. This is an important problem in music, and underlies Helen’s observations about natural sequences. (Ian Phillips has an excellent piece about this problem in the European Journal of Philosophy in 2008.)
In the case that I am describing, I don’t have a sequence of perceived events translating into a perceived sequence of events. Rather, I have the simple feeling that I have been sitting here for three hours, a simple feeling of the passage of time since a prior event. In what does this feeling consist? Is it even coherent to describe as I have been. It is not like an estimate of distance. When you estimate the distance between two pillars you are able to see both pillars. (The same, as mentioned before, holds of estimations of size.) In the case in question, I am estimating the time between two events. But I don’t, and couldn’t possibly, perceive both events. (It doesn’t help to say: I remember sitting down at 2 o’clock. I do, of course, but how does a memory of sitting down together with an awareness of rising help me estimate the time interval between the two events? Neither is time-stamped, after all.)
The problem is somewhat similar to that of perceiving motion. The fielder sees the ball moving across her field of vision. How? At any given moment, she must see the ball at a place. She cannot see where it was before—before is gone and done with. So how can she see it move? How can she compare where it was with where it is?
Seeing motion is actually future-oriented, and hence different from my example. The fielder’s visual system keeps track of where the ball has been. (This does not require her seeing where the ball has been.) On this basis, her visual system predicts where the ball will be. The fielder’s gaze and intercepting trajectory will be directed at where the ball will be, not at where it is. These bodily motions are controlled by the visual system’s anticipation of where the ball will be in a couple of moments. Since the ball won’t be where it is now, such as state of anticipation is a perception of motion. When the ball is static, the visual system doesn’t anticipate that it’ll be some place different from where it is. So in this case, it doesn’t perceive motion.
This solution won’t work for perceiving the passage of time. Feeling that I have been sitting here for three hours is not the same as anticipating anything. Since it couldn’t be a perception of anything past—the past is done and gone. This is not a memory. Rather, it is a feeling about now, namely that it is three hours since an earlier event.
The question I am asking is not metaphysical, at least not primarily. I just want to know how it can be that we have a sense of time passed. What do we need for this? (An internal clock is not enough, by the way—for I would have to remember what it said when I sat down to write, just as I would have to remember what my external watch said if I am to use it to estimate intervals of time.) I have some ideas, of course, and I am sure you do too, dear reader. (Please share.) But for now, let me simply record my puzzlement. The answer is not straightforward.