Presentism and Eternalism: Two Philosophical Theories about Time

Presentism is a theory in philosophy which says that the only events and objects which exist are those that exist in the present. So, only things which exist now, right now, really exist. It is a theory which focuses on the temporal present; that is, things existing in the present moment. It is not a theory concerned with whether things exist somewhere else. So long as that object or event which is spatially distant from us exists in the present moment, then it exists. If we were to make a list of all the things that a Presentist believes exists and does not exist; in the list of things that do exist we would have: the Grand Canyon and the Taj Mahal; whereas in the list of things that do not exist we would have: Socrates and tomorrow's events.

The philosopher Ted Sider says, “Presentism is the doctrine that only the present is real… A presentist thinks that everything is present; more generally, that, necessarily, it is always true that everything is (then) present.” With this definition, the past and future do not exist – they are not real! That is why Presentism is so mind-boggling, because we are constantly thinking about the past and planning for the future. But according to this theory, the past and future only exist subjectively – it is only the present which exists objectively (outside of our minds). Also, if we take a statement like “Newton exists”, then this statement could only be true if it was said when Newton existed in the present, say in 1666. If we say that statement now, then it is false. When making statements about what exists, the truth of the statement depends on the context (when the statement was made).

Arthur Prior is another philosopher who argues that the present is real, and the past and future unreal. He says that since it is necessarily true that only the present exists, then there is no point in referring to the present moment. Saying that something is “present” (e.g. “I am present in this room”) adds no new information to the statement, since all things which exist are present. If I exist in the room, then it follows that I must be present. So the statement should read: “I am in the room”. “Present”, as a word, Prior argues, is redundant.

Buddhist teaching also encourages people to focus on the present moment, as that is the only thing which truly matters. As the Buddha says in the Bhaddekaratta Sutta: "You shouldn't chase after the past or place expectations on the future. What is past is left behind. The future is as yet unreached. Whatever quality is present you clearly see right there, right there.” There are also Buddhist philosophers who have formulated a kind of Buddhist Presentism. One of them, Fyodor Shcherbatskoy wrote: "Everything past is unreal, everything future is unreal, everything imagined, absent, mental... is unreal... Ultimately real is only the present moment...”

There are problems with Presentism however, such as, how the theory relates to the flow of time. If time passes, then does every event not exist in the past, present, and future? If there are no events which are in the past or in the future, then how does time pass? Also, if past events are unreal, then what do photographs actually show? And what are we referring to when we talk about past events? These issues have led some to prefer the Eternalist theory of time.

Eternalism contrasts to Presentism and be thought of as its opposite. Eternalism is the philosophical theory which says that all points in time are equally real. The past, the present, and the future are all real. In this sense, Socrates and tomorrow's events exist right now, even if I cannot see them or interact with them. Many philosophers have adopted Eternalism because they argue that Presentism is contradicted by Einstein's Special and General Theory of Relativity, whereas Eternalism agrees with it. As the philosopher of science, Dean Rickles puts it: "the consensus among philosophers seems to be that special and general relativity are incompatible with presentism."

According to the Presentists, there is a flow of time, with the present moment moving forward into the future and leaving the past behind. However, this idea assumes that the present moment will be the same for everyone, an idea which runs up against special relativity. Special relativity says that observers with different frames of reference (such as observers moving at different speeds) can have different perceptions of whether a pair of events happen at the same time or at different times. In addition, someone moving faster than someone else will experience “time passing” slower than they do. The theory also says we have no reason to prefer one observer's perception to another – both are correct. We therefore cannot say that there are a set of events simultaneously happening in the present. People's “present” is different depending on their frame of reference.

In Einsteinian relativity, the “present” is not something which is an absolute element of reality. As Einstein himself said, “People like us, who believe in physics, know that the distinction between past, present, and future is only a stubbornly persistent illusion". Eternalism does not necessarily do away with the concepts of past and future, but considers them more like directions – whether something is in the past or future depends entirely on your frame of reference. Eternalism also agrees with general relativity (Einstein's theory of gravity) in which time becomes a dimension intertwined with the three dimensions of space. This is known as four dimensional space-time. Time therefore becomes part of the physical structure of the universe and things in the past or future will eternally exist, so long as the structure of the universe eternally exists. Since distinctions between the past, present and future are illusory, we can think of all objects and events as being timeless or eternal.

Even though it seems like common sense that there is a “flow of time”, Einstein argues that this is a subjective illusion. In actual fact, there is no such thing as the flow of time. The sense of this flow of time is extremely convincing, but it probably just reflects how our brains have evolved. If we did not make distinctions between the past, present and the future, perhaps this would hinder our ability to survive. In fact, looking to the past for lessons and planning for the future seem to be essential components of any survival strategy. Our brains are simply not equipped to perceive the true nature of time. Eternalism has also been described as the “Block Universe” theory, since all of the points in space-time are fixed and unchanging. Everything, in a sense, exists now. This theory does, however, have some controversial implications for free will. For example, if the future is fixed, then in what sense can I really make a conscious choice to do something?

9 comments:

  1. Great! Helped a lot with the understanding of presentism

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  2. Nice article, but does eternalism really imply hard determinism? Quantum mechanics, and in particular Aspects experimental tests of Bell's Inequality and those that follow, plus experiments on quantum entanglement, suggest that there is a truly random element in quantum interactions. Hidden variable theories are finding it very hard to explain those results. Within a block universe then while each interaction will have a definite outcome, that outcome cannot be predicted even given prefect knowledge of the preceding conditions. The real question is whether "free will" can be equated with "not predictable even in principle", or whether decisions being in part random is not free will, just noise in the machine.

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    1. I don't believe I said that eternalism implies hard determinism. But you're right, eternalism is perfectly consistent with the indeterminacy of quantum interactions. I do not believe that free will - defined in terms of 'evitability' (Daniel Dennett's definition) - is incompatible with determinism.

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    2. Thanks for replying Sam,

      My apologies if I misread our comment, I thought hard determinism was what you were alluding to when you said "[the “Block Universe” theory] .. does, however, have some controversial implications for free will. For example, if the future is fixed, then in what sense can I really make a conscious choice to do something?"

      I agree, compatibilism is another valid approach to resolving that question.

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    3. It seems to me that Many Worlds theory makes eternalism and determinism compatible with quantum mechanics. The universe is really an (eternal) set of branches. While it appears to me that something random is happening (a quantum coin is flipped) in fact there is a "heads" branch universe and a "tails" branch universe, both of which exist right now. It's just that I perceive myself to be in one branch or the other. My consciousness in the heads branch does not communicate with my consciousness in the tails branch. In this way, all actions have _multiple_ definite outcomes rather than a single random outcome.

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    4. That might be valid but within each branch, you still have the question of whether the past and future(s) have a permanent existence.

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  3. Based on what you pointed out as problems for the theory, I think you dont quite fully grasp the concept of presentism. "If time passes", you say, but that time does not "pass" is the basis of the theory in the first place. First, remember you shouldn't favor either one of these theories just realize that neither can be distinguished or "proven". Okay, before I move on to a presentist point of view, I want to make some objective statements: what you call past are memories created in your head in the present. What you call future are dreams created in your head in the present. What you call experience is based on what you have created in your head as a model of "reality". So if you are incredulous, you acknowledge that whether the past existed or not (also whether the future will exist or not), it is based on a thought in your head. Now I think it is easy to see the difference in the two theories: one, the past really happen or two, its an imagination in the eternal present. Impossible to distinguish these theories with any tests or logic, thus the existence of the two theories.

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  4. Do you have a list of sources that would be useful for further research into this?

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  5. The special theory of relativity (STR) doe NOT assume that all frame of reference are EQUALLY ontologically privileged, rather it cannot assess a privileged frame. This is an important distinction as an eternal block conception of time does not follow from STR! Rather, STR is agnostic on eternalism or presentism or growing block, as it cannot know if all frames are ontologically privileged, or if there is a single frame that is absolute. It is an epistemic problem, and one should not assume that STR means "all frames are equally ontologically privileged", as that claim would be an argument from ignorance fallacy right from the get-go.

    Also, it isn't a lack of free will that is the biggest problem for an eternal block, as a lack of free will is the case regardless (free will in the important sense is incompatible with any theory of time, as well as determinism and indeterminism. Rather, the biggest problem is that it postulates eternal dinosaurs, eternal humans, eternal airplanes, and eternal robots....that never came INTO being (they always existed along side every other event and any observation of becoming is just an illusion). This is a deep problem with eternal block conceptions.

    Thank you.

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