By Anna Prisco
We often speak of time as if it “flows.” We say: “time flies when you’re having fun,” “it’s half past eight,” “the minutes are dragging on and on,” and other idioms connected to what is called the A theory of time. After discussing how these expressions work in our language in the first section, I will point toward problems associated with this “flowing” quality of time presupposed by the A theory in the second section. In the third section, I identify a possible avenue of escape: “flowing is merely a metaphor,” clamors the naïve A theorist! To this, I argue that the presentism held by the A theorist necessarily entails “flowing” and all its non-metaphorical problems.
In the fourth section, I point toward an alternative understanding of time, the B theory, which describes time as we might describe space. The B theory, as I argue, does not run into the same metaphysical difficulties as A theory.
- How do we talk about time?
Our language is riddled with talk of the “flow” of time. This idea of time as flowing or passing serves as the foundation for the A theory of time. According to the A theory of time, the passage of time is a necessary part of the world, and statements like “one year ago” have real, objective merit. Moreover, most A-theorists also accept presentism, the idea that the only objects that exist are those objects that exist in the present. Some consequences of this theory are as follows. I can say that John F. Kennedy (the person) no longer exists, for it is not true that JFK exists in the present. This also entails the belief that the present is metaphysically privileged compared to the past and the future. For, only the present really exists. Evidence of presentism is also found in our ordinary expressions: we may be nervous for an upcoming surgery, but upon its completion we can say “thank goodness that’s over.” Our ability to express gratitude that the surgery is over is seemingly due to the fact that the surgery doesn’t exist anymore. More generally, the A theory of time is tensed and includes any tensed sentences. It holds on to the idea that something can be over, done with, or exist no more.
- Why doesn’t this work?
Though our ordinary language seems to support A theory, it’s not without its problems. Firstly, the manner through which we know that any given object is moving is dependent on time. If I were to say, “this car is moving.” the way that we would evaluate that claim would be by checking the position of that car at two distinct times, and then observing that the position of the car had changed over that period of time. Without exception, some variation of this formula can be used for us to describe the physics of motion. We define motion itself as a change in any X over time. But, we run into problems when we try to talk about time in the same way. Let’s assume A theory: time moves or flows. If time moves or flows, there must be something that we can measure its motion against. Yet our normal tool for this is time itself. Is there a special type of time that we can measure the movement of time against? Let’s assume there is and call this time T1, or hypertime. At time T, it is T1, and at time T+1, it is T2. Quickly, this leads to an infinite regress. If we must use hypertime to measure time, how should we measure hypertime? If time moves against hypertime, does hypertime move against hyper-hypertime, which moves against hyper-hyper-hypertime, and so forth?
If time can’t move against a special sort of time, can it just move against normal time? Perhaps we can set up the same scenario by which we addressed the movement of the car, but instead of two locations we have two times: t1 and t2. We then map these on to actual times, and set t1 at 1:00 pm and t2 at 4:00 pm. But this doesn’t give us any satisfactory account for the movement of time. These facts are only trivial. We know that at 1:00 pm it is 1:00 pm, and that at 4:00 pm it is 4:00 pm. We lack any sort of explanation that doesn’t refer back to itself to explain how time moves. When we try to escape the infinite regress, we end up at circularity!
- What can our A-theorist do?
Perhaps there is a way out for our A theorist. She may argue that the notion of time flowing is not to be taken literally. Maybe then she can hold on to presentism, and therefore the A theory, without conceding the problems implied by the “flow” of time. When pressed closely on how exactly time can “flow,” not all A theorists hold on tightly to that notion. Instead, many would posit that more important to the A theory is presentism itself: that to exist means to exist now in the present. By discarding the argument that time “flows,” “moves,” or “passes,” the A theorist hopes to do away with the baggage associated with these ideas. Yet it becomes apparent that these issues persist with presentism. As such, I argue A theorists must necessarily accept the “flow” of time as it is entailed by presentism. Following from presentism, what exists now is the sum total of what exists. Let’s think about this using time Х and then time X1, which is just a small fraction of a second later. Between time X and X1, virtually nothing has changed – there is no meaningful difference between the world at those two times. I hope to show with the following argument how the material continuity of the world from present moment to present moment necessarily entails a movement of time.
- The worlds Wx and Wx1 are materially continuous
- If two things are continuous, their truth makers must also be continuous.
- The truth makers of worlds Wx and Wx1 are the times X and X1, respectively
Therefore, times X and X1 are continuous.
The first premise is rather straightforward – if there is a pen on the table at time X, we assume that if we watch the pen in the nanosecond between X and X1 and detect no movement that it is the same pen. The second also shouldn’t be contentious; if there was discontinuity of the truth makers of two things (perhaps also caveating that the truth makers must be of the same type), there would be nothing to actualize the truth at a moment between two, creating a material discontinuity. The third premise is just a formalization of presentism; the truth maker of the world at time X (Wx) is the time X, for it is the reason that we can say everything in that world exists. From this naturally follows that the two times X and X1 are continuous. And because we know that X occurs before X1 and exists no longer, we know that the time has moved from X to X1. Now we see that presentism entails the flow of time. Presentists cannot adopt a view that what exists is just the present, because that idea requires some movement or flow between each infinitesimally small “present.” And I have already discussed the issues caused by adopting such a flow of time.
- How can we cope with B theory?
If we have to relinquish our common perception of time, what remains? Our rejection of A pushes us to accept what is called the B theory: we can talk about time like we do about space. If the A theory gave us a tensed existence, to exist in the B theory means to exist tenselessly. This is to say that time is spread out like a map, with every point on it existing tenselessly. With this comes a split of the person (and whatever else may exist) into their physical parts and temporal parts. I, the person, exist from 1999 until some point in the future. My temporal parts are me-at-a-time, just as I have a temporal part writing this paper in 2018, I have a temporal part learning how to walk in 2001. What I am is just the sum of my temporal parts. The B theory solves the issues associated with the A theory by creating a theory of time without movement or a privileged “now,” and for this reason it is metaphysically responsible for us to accept it.
But there are still some practical objections to the B theory that are worth considering. It may be true that the A theory is the common conception of time, therefore there are some components in it we’d rather not lose. We can take the case of my cat who died in 2004 as an example. Many argue that according to the B theory, I have no reason to be sad about my cat’s death. Why should I be? My cat exists tenselessly (along with me!) in 2004. In the A theory I can say, “I am sad because my cat doesn’t exist anymore.” Even though I might buy into B theory completely, I want to be sad that my cat isn’t alive in 2018. I believe the solution to this is the use of the subjective “now” in B theory. Although “now” is thought to belong to A theory, we can still apply the word in B theory. It’s not an objective word, but rather designates where we stand in time. Similar to space, I can say “it is 2018” and Catherine the Great can say “it is 1775” and neither of us is wrong – it’s a subjective indicator of where we stand in the timeline, just as someone might say “I’m in Chicago” and another “I’m in Russia.” While I may exist tenselessly in 2004 with my cat, I can say in 2018 something along the lines of “I am sad that my cat isn’t with me now.” For, all I am saying is that I am upset that my subjective now does not include my cat. Similarly, I might be just as sad should my cat be far away from me in space, I in Chicago and my cat in Bora Bora. This seems to represent what we mean when we express the privation of something. Instead of being upset that they don’t exist, we are just sad that the moment we are subjectively experiencing doesn’t include them.
This is just a thought towards how we may include practical expressions associated with A theory in the B theory. However, this is not strictly necessary. Our inability to find a way to translate tensed A theory statements into tenseless B theory statements is not an argument against B theory. Rather, it shows that the way we have evolved to view time is more in line with the A theory. This is nothing more than a practical argument. While it would be nice to reconcile our A theory ways of speaking with a tenseless B theory, it is not necessary. It only serves to match our common perceptions of time with a more metaphysical accuracy. If the B theory is what we must accept in order to be metaphysically responsible, perhaps this makes the pill easier to swallow.
 While it may be argued that presentism is not a necessary component of A theory, it is accepted by most A-theorists and will be considered a part of A theory for the purposes of this paper.