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“What, then, is time? If no one asks me, I know what it is. If I wish to explain it to him who asks me, I do not know.”

—Augustine 1995, Book 11

What actually is Time? Is there even something like Time outside of our concept of Time? Then, probably the most fascinating of all questions—is travel through time possible just like travel through space is? Here are some of the most basic and fundamental theories of time through history.

The concept of time present to us probably one of the most interesting problems ever tackled by the human mind. It is an intangible, conceptual thing that somehow governs all of the world, that has inserted itself into most of our basic physical formula with a simple, innocent t.

But the subject of Time is a deeply complex area of study, both scientifically and philosophically. For ages we have been trying to understand it, and then trying to control our movements through it like we can with space. We can control how fast or slow, in which direction we can move through space. We also move through time, each day, every minute, every second. The only thing is that we cannot control the speed or direction of our travel through time. And it has long been a fantasy of authors and film makers to find ways to make this atleast hypothetically possible. 

But before one can even think about time travel, one needs to atleast have an understanding of what time is.

Different positions on Time

Substantivalism is the position that time is independent of objects and events is a conception of time as a substance. In opposition to substantivalism, Relationalism claims that time is dependent on other things in some way. Time is just a property of or a set of particular relations between other things.

Immanuel Kant’s antinomies  “declaimed that either aspect of it was as capable of being proved as the other, i.e., that the world could have had and could not have had a beginning in time and an end in space”. If both arguments are equally compelling, then we cannot believe that either is true of time; each contradicts the other. Yet, if anything exists, it must either have a beginning or not have a beginning. As such, unable to be either, time cannot be anything real.

Sextus Empiricus also attacks our idea of time through this sceptical method and presents a number of arguments denying that one can have beliefs about time.

Theories of Time: Tense Vs Tenseless Time

McTaggart says that, ‘Positions in time as time appears to us prima facie, are distinguished in two ways.’

He introduces the term ‘A series’ for ‘that series of positions which runs from the far past through the near past to the present, and then from the present through the near future to the far future’, and the term ‘B series’ for ‘the series of positions which runs from earlier to later’. 

He claims that ‘the movement of time consists in the fact that later and later terms pass into the present, or—which is the same fact expressed in another way—that presentness passes to later and later terms. If we take it the first way, we are taking the B series as sliding along a fixed A series. If we take it the second way, we are taking the A series as sliding along a fixed B series.

Imagine a rope stretched across time and imagine points specified on this rope like tiny ropeways that can move from one place to the next. According to one viewpoint, the ropeway moves from the far past to past to present to future and then to far future. On the other view, the ropeway goes simply form earlier to later.

Furthermore, McTaggart argues that the B series (earlier to later) presupposes the A series (past to future), rather than vice versa. His argument starts from the fact that ‘time involves change’, and that the only way in which events can change is in respect of their A-characteristics. And he ends up concluding that time cannot be real.

A-theory or Tense theory is the position that time and change are fundamentally tensed or composed of A-series positions. Tense theory differs from McTaggart in also holding that such fundamentally tensed time is real.

Tenseless theory is the theory that the A-series is not fundamental to time or change. As such, neither is a unique present or temporal passage. Events do not need to change A-series positions for there to be real change.

If you want to read more on the A and B series, I would really recommend reading the section on McTaggart from Sean Edna Power’s Philosophy of Time.

Presentism and Eternalism

The core tenet of Presentism is that the present of the real, fundamental Aseries is all that there is. The present encapsulates all of reality. Reality is wholly confined to that single time. If some X is real, then X is in the real present. In contrast, any X that is past or future is unreal. Like unicorns or dragons, past dinosaurs are not real and future humans are not real.

P is a claim about what exists (what there is), absolutely and unrestrictedly. As a description of presentism, it’s both mainstream and minimal. 

To flesh out the ontological thesis, P is often contrasted with two other ontological theses: an opposing view of time, Eternalism (“past, present, and future things exist”), and an analogical view in modality, Actualism (“only actual things exist”)

Presentism is the temporal analogue of the modal doctrine of Actualism, according to which everything is actual. The opposite view in the philosophy of modality is Possibilism, according to which non actual things exist; its temporal analogue is Eternalism, according to which there are such things as merely past and merely future entities.

Eternalism is the position that not only present things are real. Things at other times, both earlier and later than the present, are also real. Broadly speaking, presentism is a common-sensical view, and it also aligns with our manifest image of time. When we imagine time, atleast when I imagine time, I imagine it as a series of stones materialising in front of me as I keep stepping forward. Only that point exists on which my feet rests. The one behind disappear as soon as I step forward and the ones after haven’t yet come to being real. 

The primary motivation for eternalism, however,  arises from orthodox interpretations of the theories of relativity. According to them, simultaneity is relative, not absolute. This implies that there is no universal ‘now’ stretched out across the entire universe. One observer’s present can be another’s past or future. Assuming the universe is four-dimensional spacetime, then all events exist unconditionally.

The two kinds of eternalism are as follows:

The “Moving Spotlight” theory holds the real present, and change in relation to it, is explained by there being a singular moment—the present—that changes in relation to everything else. Events do not change; instead, the present changes. It changes by being first at one set of events, then being at another set of events, and then yet another set of events and so on.

A second ‘Growing Block Theory’ holds that while the present and past are real, but the future is not real. Central to the idea of the growing block theory is that real change is an increase in what is real: the number of past events constantly increases while the events that are present constantly change. However, one disadvantage of the growing block is that it is more complex than both presentism and the moving spotlight.

To Conclude

While there may be many positions on the apparent existence or non existent of an absolute, independent Time, there remains an essential, inherent insufficiency in our perception that cannot simply be transcended. As humans limited by sense organs and mind, we simply cannot perceive the objective and absolute as it is without rendering it, in some way, subjective. 

There is no method of confirming the existence of the object except through inference and reason. And yet, disproving a thing merely because there is no empirical method of proving it seems contrary and arrogant to an extreme. 

If you liked this post, we would also recommend Sylvia Plath’s Fig Tree Analogy: Can We Choose The Best Life?

Next up: Is Time Travel Possible? Should it be??