Block time
Encyclopedia
Eternalism is a philosophical
approach to the ontological
nature of time
, which takes the view that all points in time are equally "real", as opposed to the presentist
idea that only the present is real. Modern advocates often take inspiration from the way time is modeled as a dimension
in the theory of relativity
, giving time a similar ontology
to that of space
(although the basic idea dates back at least to McTaggart's
B-Theory of time
, first published in The Unreality of Time
in 1908, only three years after the first paper on relativity). This would mean that time is just another dimension, that future
events are "already there", and that there is no objective
flow of time. It is sometimes referred to as the "block time" or "block universe" theory due to its description of space-time as an unchanging four-dimensional "block", as opposed to the view of the world as a three-dimensional space modulated by the passage of time.
", the "present", and the "future
". Using that representational model, the past is generally seen as being immutably fixed, and the future as undefined and nebulous. As time passes, the moment that was once the present becomes part of the past; and part of the future, in turn, becomes the new present. In this way time is said to pass, with a distinct present moment "moving" forward into the future and leaving the past behind. This view of time is given the name presentism
by philosophers.
This conventional model presents a number of difficult philosophical problems, and seems difficult to reconcile with currently accepted scientific theories such as the theory of relativity
.
has shown that the concept of simultaneity
is not universal: observers in different frames of reference
can have different perceptions of whether a given pair of events happened at the same time or at different times, with there being no physical basis for preferring one frame's judgments over another's (though in a case where one event A happens in the past light cone
of another event B, all frames will agree that A happened in the past of B). So, in special relativity there can be no physical basis for picking out a unique set of events that are all happening simultaneously in "the present".
, J. M. E. McTaggart
divided time into an A-series and a B-series
, with the A-series describing events in absolute tensed terms (past, present, and future) and the B-series describing events in terms of untensed temporal relations (before and after). He went on to argue that the A-series was logically incoherent and should be discarded, and that the B-series was insufficient for a proper understanding of time. He endorsed the C-series instead, which is a fixed, changeless (and therefore timeless), non-directional ordering of events. While McTaggart's concluded that time is unreal, various philosophers and physicists have held that the remaining B-series is all that is needed for a complete theory of time, sometimes referred to as the B-Theory of time
.
Since an observer at any given point in time can only remember events that are in the past relative to him, and not events that are in the future relative to him, the subjective illusion of the passage of time is maintained. The asymmetry of remembering past events but not future ones, as well as other irreversible events that progress in only one temporal direction (such as the increase in entropy
) gives rise to the arrow of time
. In the view suggested by Eternalism, there is no passage of time; the ticking of a clock measures durations between events much as the marks on a measuring tape measures distances between places.
Eternalism may have implications for the concept of free will
, in that it proposes that future events are as immutably fixed and impossible to change as past events (see determinism
). However as the human subject, and any free will they have, is also 'present' throughout time, during their life, they may be exercising free will in the 'future' as it were.
Eternalism makes two assumptions, which are separable. One is that time is a full-fledged real dimension
. The other is immutability. The latter is not a necessary consequence of the first. A universe in which random changes are possible may be indistinguishable from the many-worlds interpretation
of quantum mechanics in which there are multiple "block times."
Augustine of Hippo
wrote that God
is outside of time
—that time exists only within the created universe. Many theologians agree. On this view, God would perceive something like a block universe, while time might appear differently to us finite beings.
argue that "The Block universe gives a deeply inadequate view of time. It fails to account for the passage of time, the pre-eminence of the present, the directedness of time and the difference between the future and the past"
The comment summarizes the main objections. In more detail, they are:
future (which nonetheless does not exist at the present) would not satisfy common-sense intuitions about time. If indeterminism can be removed from flow-of-time theories, can it be added to Eternalist theories? Surprisingly, the answer is a qualified "yes" in the form of multiverse
theories, where multiple alternate futures exist in a fixed framework, but individual observers have no way of knowing which alternative, or "branch" they will end up in.
[* Another, perhaps more compelling, explanation for this difference of attitudes would be that it really is worse to be having a bad experience than to have had one. A bad experience in the future is seen as one that has not been had, but will be. Unfortunately for Eternalism, though, it appears to lack the conceptual apparatus needed to explain 'having an experience', as distinct from having had, or being about to have, that experience. This is why most people find Eternalism strongly counter-intuitive.]
, in which the relativity of simultaneity is used to show that each point in the universe can have a different set of events that are in its present moment. According to Presentism
this is impossible because there is only one present moment that is instantaneous and encompasses the entire universe.
Some philosophers also appeal to a specific theory which is "timeless" in a more radical sense than the rest of physics, the theory of quantum gravity
. This theory is used, for instance, in Julian Barbour
's theory of timelessness. On the other hand, George Ellis argues that time is absent in cosmological theories because of the details they leave out.
, a special term Dharmadhatu
is translated as 'total field of events and meanings' or 'field of all events and meanings.' Here the 'Block Universe' seems to be encompassing not only every possible event in the physical universe but also having a psychological component.
See: Śūnyatā, section "Eternalism"
’s novel, Slaughterhouse-Five
. The Tralfamadorians, an alien species in the novel, have a four-dimensional sight and can therefore see all points in time simultaneously. They explain that since all moments exist simultaneously, everyone is always alive. The hero, Billy Pilgrim, lives his life out of sequence, which, among other things, means that his point of death occurs at a random point in his life rather than at the end of it.
Eternalism also appears in the comic book series Watchmen
by Alan Moore
. In one chapter, Dr. Manhattan explains how he perceives time. Since past, present, and future events all occur at the "same time" for him, he speaks about them all in the present tense. For example, he says "Forty years ago, cogs rain on Brooklyn" referring to an event in his youth when his father throws old watch parts out a window. His last line of the series is "Nothing ends, Adrian. Nothing ever ends."
Philosophy
Philosophy is the study of general and fundamental problems, such as those connected with existence, knowledge, values, reason, mind, and language. Philosophy is distinguished from other ways of addressing such problems by its critical, generally systematic approach and its reliance on rational...
approach to the ontological
Ontology
Ontology is the philosophical study of the nature of being, existence or reality as such, as well as the basic categories of being and their relations...
nature of time
Philosophy of space and time
Philosophy of space and time is the branch of philosophy concerned with the issues surrounding the ontology, epistemology, and character of space and time. While such ideas have been central to philosophy from its inception, the philosophy of space and time was both an inspiration for and a...
, which takes the view that all points in time are equally "real", as opposed to the presentist
Presentism (philosophy of time)
Saint Augustine proposed that the present is a knife edge between the past and the future and could not contain any extended period of time. This seems evident because, if the present is extended, it must have separate parts - but these must be simultaneous if they are truly part of the present...
idea that only the present is real. Modern advocates often take inspiration from the way time is modeled as a dimension
Dimension
In physics and mathematics, the dimension of a space or object is informally defined as the minimum number of coordinates needed to specify any point within it. Thus a line has a dimension of one because only one coordinate is needed to specify a point on it...
in the theory of relativity
Theory of relativity
The theory of relativity, or simply relativity, encompasses two theories of Albert Einstein: special relativity and general relativity. However, the word relativity is sometimes used in reference to Galilean invariance....
, giving time a similar ontology
Ontology
Ontology is the philosophical study of the nature of being, existence or reality as such, as well as the basic categories of being and their relations...
to that of space
Space
Space is the boundless, three-dimensional extent in which objects and events occur and have relative position and direction. Physical space is often conceived in three linear dimensions, although modern physicists usually consider it, with time, to be part of a boundless four-dimensional continuum...
(although the basic idea dates back at least to McTaggart's
J. M. E. McTaggart
John McTaggart was an idealist metaphysician. For most of his life McTaggart was a fellow and lecturer in philosophy at Trinity College, Cambridge. He was an exponent of the philosophy of Hegel and among the most notable of the British idealists.-Personal life:J. M. E. McTaggart was born in 1866...
B-Theory of time
B-Theory of time
The B-theory of time is a term, given to one of two positions taken by theorists, in the philosophy of time. The labels, A-theory and B-theory, are derived from the analysis of time and change developed by Cambridge philosopher J. M. E...
, first published in The Unreality of Time
The Unreality of Time
The Unreality of Time is the best-known philosophical work of the Cambridge idealist J. M. E. McTaggart. In the paper, first published in 1908 in Mind 17: 457-73, McTaggart argues that time is unreal because our descriptions of time are either contradictory, circular, or insufficient...
in 1908, only three years after the first paper on relativity). This would mean that time is just another dimension, that future
Future
The future is the indefinite time period after the present. Its arrival is considered inevitable due to the existence of time and the laws of physics. Due to the nature of the reality and the unavoidability of the future, everything that currently exists and will exist is temporary and will come...
events are "already there", and that there is no objective
Objectivity (science)
Objectivity in science is a value that informs how science is practiced and how scientific truths are created. It is the idea that scientists, in attempting to uncover truths about the natural world, must aspire to eliminate personal biases, a priori commitments, emotional involvement, etc...
flow of time. It is sometimes referred to as the "block time" or "block universe" theory due to its description of space-time as an unchanging four-dimensional "block", as opposed to the view of the world as a three-dimensional space modulated by the passage of time.
Problems with the flow of time
Conventionally, time is divided into three distinct regions; the "pastPast
Most generally, the past is a term used to indicate the totality of events which occurred before a given point in time. The past is contrasted with and defined by the present and the future. The concept of the past is derived from the linear fashion in which human observers experience time, and is...
", the "present", and the "future
Future
The future is the indefinite time period after the present. Its arrival is considered inevitable due to the existence of time and the laws of physics. Due to the nature of the reality and the unavoidability of the future, everything that currently exists and will exist is temporary and will come...
". Using that representational model, the past is generally seen as being immutably fixed, and the future as undefined and nebulous. As time passes, the moment that was once the present becomes part of the past; and part of the future, in turn, becomes the new present. In this way time is said to pass, with a distinct present moment "moving" forward into the future and leaving the past behind. This view of time is given the name presentism
Presentism (philosophy of time)
Saint Augustine proposed that the present is a knife edge between the past and the future and could not contain any extended period of time. This seems evident because, if the present is extended, it must have separate parts - but these must be simultaneous if they are truly part of the present...
by philosophers.
This conventional model presents a number of difficult philosophical problems, and seems difficult to reconcile with currently accepted scientific theories such as the theory of relativity
Theory of relativity
The theory of relativity, or simply relativity, encompasses two theories of Albert Einstein: special relativity and general relativity. However, the word relativity is sometimes used in reference to Galilean invariance....
.
Simultaneity
Special relativitySpecial relativity
Special relativity is the physical theory of measurement in an inertial frame of reference proposed in 1905 by Albert Einstein in the paper "On the Electrodynamics of Moving Bodies".It generalizes Galileo's...
has shown that the concept of simultaneity
Simultaneity
Simultaneity is the property of two events happening at the same time in at least one frame of reference. The word derives from the Latin simul, at the same time plus the suffix -taneous, abstracted from spontaneous .The noun simult means a supernatural coincidence, two or more divinely...
is not universal: observers in different frames of reference
Frame of reference
A frame of reference in physics, may refer to a coordinate system or set of axes within which to measure the position, orientation, and other properties of objects in it, or it may refer to an observational reference frame tied to the state of motion of an observer.It may also refer to both an...
can have different perceptions of whether a given pair of events happened at the same time or at different times, with there being no physical basis for preferring one frame's judgments over another's (though in a case where one event A happens in the past light cone
Light cone
A light cone is the path that a flash of light, emanating from a single event and traveling in all directions, would take through spacetime...
of another event B, all frames will agree that A happened in the past of B). So, in special relativity there can be no physical basis for picking out a unique set of events that are all happening simultaneously in "the present".
Uniqueness of a present moment
There is no fundamental reason why a particular "present" should be more valid than any other; observers at any point in time will always consider themselves to be in the present. However, every moment of time has a "turn" at being a present moment in flow-of-time theories, so the situation ends up symmetrical. Although there is still an ontological distinction between past, future, and present that is not symmetrical.Rate of flow
The concept of "time passing" can be considered to be internally inconsistent, by asking "how much time goes by in an hour?" However, the question could be no different from "how much space is contained in a meter?" — all measurements being equally arbitrary.McTaggart's argument
In The Unreality of TimeThe Unreality of Time
The Unreality of Time is the best-known philosophical work of the Cambridge idealist J. M. E. McTaggart. In the paper, first published in 1908 in Mind 17: 457-73, McTaggart argues that time is unreal because our descriptions of time are either contradictory, circular, or insufficient...
, J. M. E. McTaggart
J. M. E. McTaggart
John McTaggart was an idealist metaphysician. For most of his life McTaggart was a fellow and lecturer in philosophy at Trinity College, Cambridge. He was an exponent of the philosophy of Hegel and among the most notable of the British idealists.-Personal life:J. M. E. McTaggart was born in 1866...
divided time into an A-series and a B-series
A-series and B-series
A-series and B-series are two different descriptions of the temporal ordering relation among events. The two series differ principally in their use of tense to describe the temporal relation between events...
, with the A-series describing events in absolute tensed terms (past, present, and future) and the B-series describing events in terms of untensed temporal relations (before and after). He went on to argue that the A-series was logically incoherent and should be discarded, and that the B-series was insufficient for a proper understanding of time. He endorsed the C-series instead, which is a fixed, changeless (and therefore timeless), non-directional ordering of events. While McTaggart's concluded that time is unreal, various philosophers and physicists have held that the remaining B-series is all that is needed for a complete theory of time, sometimes referred to as the B-Theory of time
B-Theory of time
The B-theory of time is a term, given to one of two positions taken by theorists, in the philosophy of time. The labels, A-theory and B-theory, are derived from the analysis of time and change developed by Cambridge philosopher J. M. E...
.
The Eternalist alternative
Eternalism addresses these various difficulties by considering all points in time to be equally valid frames of reference—or equally "real", if one prefers. It does not do away with the concept of past and future, but instead considers them directions rather than states of being; whether some point in time is in the future or past is entirely dependent on which frame of reference you are using as a basis for observing it.Since an observer at any given point in time can only remember events that are in the past relative to him, and not events that are in the future relative to him, the subjective illusion of the passage of time is maintained. The asymmetry of remembering past events but not future ones, as well as other irreversible events that progress in only one temporal direction (such as the increase in entropy
Entropy
Entropy is a thermodynamic property that can be used to determine the energy available for useful work in a thermodynamic process, such as in energy conversion devices, engines, or machines. Such devices can only be driven by convertible energy, and have a theoretical maximum efficiency when...
) gives rise to the arrow of time
Arrow of time
The arrow of time, or time’s arrow, is a term coined in 1927 by the British astronomer Arthur Eddington to describe the "one-way direction" or "asymmetry" of time...
. In the view suggested by Eternalism, there is no passage of time; the ticking of a clock measures durations between events much as the marks on a measuring tape measures distances between places.
Eternalism may have implications for the concept of free will
Free will
"To make my own decisions whether I am successful or not due to uncontrollable forces" -Troy MorrisonA pragmatic definition of free willFree will is the ability of agents to make choices free from certain kinds of constraints. The existence of free will and its exact nature and definition have long...
, in that it proposes that future events are as immutably fixed and impossible to change as past events (see determinism
Determinism
Determinism is the general philosophical thesis that states that for everything that happens there are conditions such that, given them, nothing else could happen. There are many versions of this thesis. Each of them rests upon various alleged connections, and interdependencies of things and...
). However as the human subject, and any free will they have, is also 'present' throughout time, during their life, they may be exercising free will in the 'future' as it were.
Eternalism makes two assumptions, which are separable. One is that time is a full-fledged real dimension
Dimension
In physics and mathematics, the dimension of a space or object is informally defined as the minimum number of coordinates needed to specify any point within it. Thus a line has a dimension of one because only one coordinate is needed to specify a point on it...
. The other is immutability. The latter is not a necessary consequence of the first. A universe in which random changes are possible may be indistinguishable from the many-worlds interpretation
Many-worlds interpretation
The many-worlds interpretation is an interpretation of quantum mechanics that asserts the objective reality of the universal wavefunction, but denies the actuality of wavefunction collapse. Many-worlds implies that all possible alternative histories and futures are real, each representing an...
of quantum mechanics in which there are multiple "block times."
Augustine of Hippo
Augustine of Hippo
Augustine of Hippo , also known as Augustine, St. Augustine, St. Austin, St. Augoustinos, Blessed Augustine, or St. Augustine the Blessed, was Bishop of Hippo Regius . He was a Latin-speaking philosopher and theologian who lived in the Roman Africa Province...
wrote that God
God
God is the English name given to a singular being in theistic and deistic religions who is either the sole deity in monotheism, or a single deity in polytheism....
is outside of time
Eternity
While in the popular mind, eternity often simply means existence for a limitless amount of time, many have used it to refer to a timeless existence altogether outside time. By contrast, infinite temporal existence is then called sempiternity. Something eternal exists outside time; by contrast,...
—that time exists only within the created universe. Many theologians agree. On this view, God would perceive something like a block universe, while time might appear differently to us finite beings.
Philosophical objections
Philosophers such as John LucasJohn Lucas (philosopher)
- Overview :John Lucas was educated at Winchester College and Balliol College, Oxford, where he studied first mathematics, then Greats , obtaining first class honors, and proceeding to an MA in Philosophy in 1954. He spent the 1957-58 academic year at Princeton University, deepening his...
argue that "The Block universe gives a deeply inadequate view of time. It fails to account for the passage of time, the pre-eminence of the present, the directedness of time and the difference between the future and the past"
The comment summarizes the main objections. In more detail, they are:
Subjective sense of flow
Whilst the idea that there is some objective sense in which time is flowing can be denied, the fact that conscious beings feel as though it is in some sense flowing cannot. However, if the flow of time didn't have an objective existence, then it is argued conscious beings would simultaneously experience all moments in their lives. A response is that since the brain presumably perceives time through information processing of external stimuli, not by extrasensory perception, and obeys the laws of causality, it is hard to see how the flow of time, whether it exists or not, could make any subjective difference: all conscious beings are built to perceive time as a chain of events, whether or not it occurs as such.Apparent differences between past, present and future
Many of our common-sense attitudes treat the past, present and future differently.- We apparently fear death because we believe that we will no longer exist after we die. But if Eternalism is correct, death is just one of our temporal borders, and should be no more worrisome than birth.
- You are about to go to the dentist, or you have already been. Commonsense says you should prefer to have been. But if Eternalism is correct, it shouldn't matter which situation you're in.
- When some unpleasant experience is behind us, we feel glad that it is over. But if the Eternalism is correct, there is no such property as being over or no longer happening now—it continues to exist timelessly.
Status of conscious observers
Eternalists often appeal to the idea that the flow of time is a subjective illusion. However, Eternalism takes its inspiration from physics and needs to give a physical account of observers. One could, for instance, portray conscious observers as moving through the block universe, in some physically inexplicable way, in order to account for the subjective sense of a flow of time. But there is no need to do so to explain the subjective flow of time. Their opponents claim that the time-flow itself, as an objective phenomenon, is physically inexplicable, and that physics is simply misrepresenting time in treating it as a dimension.Determinism and indeterminism
Previously, it was noted that people tend to have very different attitudes towards the past and the future. This might be explained by an underlying attitude that the future is not fixed, but can be changed, and is therefore worth worrying about.* If that is correct, the flow of time is perhaps less important to our intuitions than an open, undetermined, future. In other words, a flow-of-time theory with a strictly determinedDeterminism
Determinism is the general philosophical thesis that states that for everything that happens there are conditions such that, given them, nothing else could happen. There are many versions of this thesis. Each of them rests upon various alleged connections, and interdependencies of things and...
future (which nonetheless does not exist at the present) would not satisfy common-sense intuitions about time. If indeterminism can be removed from flow-of-time theories, can it be added to Eternalist theories? Surprisingly, the answer is a qualified "yes" in the form of multiverse
Multiverse
The multiverse is the hypothetical set of multiple possible universes that together comprise all of reality.Multiverse may also refer to:-In fiction:* Multiverse , the fictional multiverse used by DC Comics...
theories, where multiple alternate futures exist in a fixed framework, but individual observers have no way of knowing which alternative, or "branch" they will end up in.
[* Another, perhaps more compelling, explanation for this difference of attitudes would be that it really is worse to be having a bad experience than to have had one. A bad experience in the future is seen as one that has not been had, but will be. Unfortunately for Eternalism, though, it appears to lack the conceptual apparatus needed to explain 'having an experience', as distinct from having had, or being about to have, that experience. This is why most people find Eternalism strongly counter-intuitive.]
Relation to physics
Eternalism takes its inspiration from physics, especially the Rietdijk-Putnam argumentRietdijk-Putnam Argument
In philosophy, the Rietdijk–Putnam argument, named after C. W. Rietdijk and Hilary Putnam, uses 20th-century findings in physics—specifically in special relativity—to support the philosophical position known as four-dimensionalism....
, in which the relativity of simultaneity is used to show that each point in the universe can have a different set of events that are in its present moment. According to Presentism
Presentism
Presentism may refer to:* Presentism * Presentism...
this is impossible because there is only one present moment that is instantaneous and encompasses the entire universe.
Some philosophers also appeal to a specific theory which is "timeless" in a more radical sense than the rest of physics, the theory of quantum gravity
Quantum gravity
Quantum gravity is the field of theoretical physics which attempts to develop scientific models that unify quantum mechanics with general relativity...
. This theory is used, for instance, in Julian Barbour
Julian Barbour
Julian Barbour is a British physicist with research interests in quantum gravity and the history of science.Since receiving his Ph.D. degree on the foundations of Einstein's general theory of relativity at the University of Cologne in 1968, Barbour has supported himself and his family without an...
's theory of timelessness. On the other hand, George Ellis argues that time is absent in cosmological theories because of the details they leave out.
Relation to Eastern body of thought
In BuddhismBuddhism
Buddhism is a religion and philosophy encompassing a variety of traditions, beliefs and practices, largely based on teachings attributed to Siddhartha Gautama, commonly known as the Buddha . The Buddha lived and taught in the northeastern Indian subcontinent some time between the 6th and 4th...
, a special term Dharmadhatu
Dharmadhatu
Dharmadhatu may be defined as the 'dimension', 'realm' or 'sphere' of Dharma and denotes the collective 'one-taste' dimension of Dharmata.-Nomenclature, orthography and etymology:...
is translated as 'total field of events and meanings' or 'field of all events and meanings.' Here the 'Block Universe' seems to be encompassing not only every possible event in the physical universe but also having a psychological component.
See: Śūnyatā, section "Eternalism"
In fiction
Eternalism is a major theme in Kurt VonnegutKurt Vonnegut
Kurt Vonnegut, Jr. was a 20th century American writer. His works such as Cat's Cradle , Slaughterhouse-Five and Breakfast of Champions blend satire, gallows humor and science fiction. He was known for his humanist beliefs and was honorary president of the American Humanist Association.-Early...
’s novel, Slaughterhouse-Five
Slaughterhouse-Five
Slaughterhouse-Five, or The Children's Crusade: A Duty-Dance with Death is a satirical novel by Kurt Vonnegut about World War II experiences and journeys through time of a soldier called Billy Pilgrim...
. The Tralfamadorians, an alien species in the novel, have a four-dimensional sight and can therefore see all points in time simultaneously. They explain that since all moments exist simultaneously, everyone is always alive. The hero, Billy Pilgrim, lives his life out of sequence, which, among other things, means that his point of death occurs at a random point in his life rather than at the end of it.
Eternalism also appears in the comic book series Watchmen
Watchmen
Watchmen is a twelve-issue comic book limited series created by writer Alan Moore, artist Dave Gibbons, and colourist John Higgins. The series was published by DC Comics during 1986 and 1987, and has been subsequently reprinted in collected form...
by Alan Moore
Alan Moore
Alan Oswald Moore is an English writer primarily known for his work in comic books, a medium where he has produced a number of critically acclaimed and popular series, including Watchmen, V for Vendetta, and From Hell...
. In one chapter, Dr. Manhattan explains how he perceives time. Since past, present, and future events all occur at the "same time" for him, he speaks about them all in the present tense. For example, he says "Forty years ago, cogs rain on Brooklyn" referring to an event in his youth when his father throws old watch parts out a window. His last line of the series is "Nothing ends, Adrian. Nothing ever ends."