Time Travel and Problems it Raises for Catholics
By Jeremy Hausotter
Apr. 11, 2021
Note on the Text:
This article was originally intended to be a chapter of a book on Catholicism and science. That project was scrapped, but not before this article and a couple others were written.
Table of Contents
2. A Sketch of Time
2.1. The Philosophical Dimension
2.2. The Theological Dimension
2.2.1. A Threefold Distinction
2.2.2. Time and Creation
3. The Meaning of Time Travel
3.1. Time Travel into the Past
3.1.1. The Problem of History
3.1.2. God and Time Travel into the Past
3.2. Time Travel into the Future
Time travel is a necessary component to many science fiction films and television shows. The genre at this point is oversaturated with time travel plot devices. Over the abundance of this device is both beneficial and harmful for the same reason: these depictions present the absurdities implied by time travel, as for example when multiple copies of a person from different moments of his life join together in a current timeline to fight the antagonist.
The proliferation of these types of plots are a testament to how captivating such a notion is. There is something seductive, almost a temptation. Between myth and history, time travel has proved to be quite fruitful for the human imagination.
Time travel is a predominant cultural expression, integrated within the American consciousness. This naturally raises questions. It makes oneself wonder whether time travel is in fact possible. If it is, then what are the consequences of this belief? What does this imply about reality? In order to answer these questions concerning time travel, we must first embark upon a theological and philosophical analysis in order to understand the nature of time and the implications time travel poses for the Catholic faith. Such an investigation requires us to face the task of clarifying what is meant by time travel. There are different modalities of time travel that require our investigation into their claims and theological implications as to how such views relate to the Catholic understanding of God and His nature. And so, we begin with a preliminary analysis of time.
2. A Sketch of Time
Our first task is determining what is time. Such an investigation is naturally limited since our investigation is preliminary for the purposes of addressing the problem of time travel and not developing a worked out philosophical-theological theory of time. Some questions are obviously avoided, such as the debate between the A and B theories of time.
We must first appreciate the fact that there are many modalities of time. We will investigate some, mention others, but by no means do we claim to have identified every modality nor to have conducted an exhaustive examination of every time modality. These raise important theological questions. We must ask ourselves questions such as does God experience time? Is time eternal or did it have a beginning? Such questions take us to the heart of Catholic dogma. We hence begin with a brief philosophical sketch that naturally draws us towards the theological dimension.
2.1. The Philosophical Dimension
Common ground across physics, philosophy, and theology is grounded in a basic intuition of the nature of time. Aristotle defined time as “the number of movement” and in a modern physics textbook we read: “time is change, or the interval over which change occurs. It is impossible to know that time has passed unless something changes.” St. Thomas likewise stated that “time is the proper measure of movement.” From ancients to moderns, we find a common insight into time's relationship to motion as the measurement of change. It is no wonder then that philosophers like Peter Kreeft defined time as “the measurement of change.”
Even though there appears to be an unanimity in understanding what time is in these multivaried disciplines, disagreements nevertheless arise as to what this basic insight means. We must ask ourselves questions such as how does this definition stand on its own? It is certainly true that time has something to do with change, but disagreements immediately arise once the question is asked what do we mean by change? There are several modalities of change that need further specification. For example, as I sit here writing this essay, I have had several thoughts. My mental state has changed from one thought to another. Emotions are another example. An insidious word can transform a calm disposition to a towering rage. These examples, however, are not what authors usually have in mind when they talk about time and change today.
Time today usually refers to changes that are extrasubjective, that is, outside the subject. Some authors then abuse the term “objective” and call this kind of time “objective time”. In physics the problem of time is presented in questions such as how long did it take for a particle to travel from one point in space to another? Here the question of change is answered strictly identified in terms of physical motion. Such a perspective can be grounded in Aristotle’s meaning of time here but we must be careful. Motion as understood in physics is only concerned with physical motion and efficient causality. This is a particular case of what Aristotle had in mind. What Aristotle understood by motion actually has a wider meaning than it does in modern physics.
Motion for Aristotle is any realization of some potency to actuality which includes much more than only physical motion. If time is understood in the broader Aristotelian schema to include any change from potency to actuality, then time itself has many more kinds of manifestations than what modern physics concerns itself within its investigations of the motion of matter.
To understand time then, one cannot simply interpret it as an extrasubjective phenomenon. Any reductionistic attempt at interpreting time as only extrasubjective or by restricting time to a mystery for the modern physicist to unravel ignores many important facets and modalities of time; most especially the meaning of time for the human person. The personal meaning of time can be taken in many different ways. History is one example, the declaration of love of a man to a woman is another. This personal meaning can be of a different kind that takes into account the subject’s perceptions of time. Time can be applied to one’s subjective life, the realm of thoughts, emotions, dreams, and aspirations, or simply the experiencing of a single minute as an enduring eternity or the rush of love and warmth with your beloved such that a summer’s day is here and gone in a flash. The personal meaning of time raises important theological questions of salvation history, man’s eternal life with God, and the relationship between time and God and angelic beings.
When we consider the problem of time travel, time is usually approached from the perspective of modern physics. Located within this scheme is likewise the drama of human history. The problems of time travel often invoke paradoxes such as if you were to go back in time and kill your father before you were born, would you then cease to exist? Or can you travel back in time and meet your past self? How much Narcissus would have desired such opportunities.
A fundamental problem with such characterizations of time travel is that these scenarios like those mentioned above reduce the human person to being strictly a temporal being. Man is reduced from being a thing that exists in of itself to a thing that exists only as a temporal being. Man is essentially reduced to the metaphysical status of a process that terminates upon completion. When a song is played, the song “exists”, but when it is finished, the song is over. The song in some meaning is a temporal being. Its act of existence depends on being performed in time over a period of time. The paradoxes suggested above in introducing the notion of time travel similarly reduce man to a temporal being like a song or sports game. One could say then that man is constituted in time by time. Such a misconception can be clearly rejected on the grounds that man is a body-soul unity which exists as a thing itself not constituted by time, but persists through time. The problem of time as presented by the concept of time travel imposes the view that all of existence is fundamentally reduced to time. Martin Heidegger, Nicolai Hartmann, and Alfred Whitehead are examples of this radical ontology. This exposed problem is the philosophical debate between perdurantism and endurantism. The perdurantists view the human person to be a strictly temporal being.
An introductory argument against time travel, at least time travel into the past, can be made here on the grounds that some types of beings cannot be rewound or replayed like a song or movie. The ability to time travel as depicted in some movies implies that all existent objects are like movies and music whose act of existence is bound to time, which would be absurd because many things exist in of themselves.
One could reply that perhaps a person is instead like a baseball game. Each baseball game is unique in that it exists for only one time interval before perishing into pastness. To this we can reply that the nature of a game is that there are agents participating in the game in order for the game to exist. It would however be absurd to claim that such is the case of a human person. If everyone in a game quit playing, the game itself ceases to exist, but there is no analogous act an agent can perform to quit a human person. There is no analogous walking off a game field that results in the nonexistence of another human person.
2.2. The Theological Dimension
One of the first theological questions asked about time is whether God is a being in time? A threefold distinction made between time, aeviternity, and eternity will enlighten us as to why the Catholic Church teaches that God is a Being outside of time who nevertheless interacts within time. There is an unfortunate trend today led by some eminent scholars and philosophers to claim that God must be a being within time and within the universe. Such a view we will see why the Catholic must reject on dogmatic grounds.
2.2.1. A Threefold Distinction
The Aristotelian notion of motion we mentioned had a much broader meaning that it does in modern physics; for Aristotle and his followers, motion is the movement from potency to act. Movement from potency to act includes many more phenomena than physical motion. For example, when one has a thought or performs a volitional act, this can be interpreted as a movement from potency to act. This means that on the basis of an Aristotelian framework of time and motion we can conclude that the inner life of the subject, the created person, has its own kind or modality of time. It is precisely such an insight that St. Thomas makes the object of one of his many investigations in his Summa Theologica.
In the Summa Theologica St. Thomas makes a threefold distinction between time, aeviternity, and eternity. The distinction between eternity and time rests on the distinction between potency and act. God alone experiences eternity because God alone is pure Being, pure Act. Time, on the other hand, measures all movements from potency to act. Time is therefore something every existent being within the universe “experiences” since everything inside the universe undergoes some kind of movement from potency to act. This is due to everything within the universe and the universe itself being created being. In eternity, on the other hand, there is no change, no movement from potency to act. God does not change. He simply exists.
Time is also distinguished from aeviternity. Aeviternity is “time” as experienced by the angels. Man does not experience aeviternity while on earth, but does experience something like it when he enters the disembodied state between his time of death and the resurrection. The angels experience aeviternity because they are not God, not pure Act, so they cannot experience eternity, while, on the other hand, they are not corporeal beings like man since angels are immaterial beings. Angels however still experience a movement from potency to act in their intellect and will, and it is this movement of their intellect and will which defines aeviternity. Aeviternity is the measurement of changes from potency to act in the rational mind of angels. The distinction between time and aeviternity also arises in terms of human conscious experience versus angelic. Man’s consciousness is like a continuous function. A continuous function has no breaks. It is a seamless line. Angelic consciousness, on the other hand, is like a discrete function, which is broken up into individual values. Each moment an angel has a movement of the intellect or will would be like a separate value in the discrete function. One can imagine a series of dots versus a solid line to further illustrate this difference.
What is remarkable about this distinction between time and aeviternity is the fact that it is grounded in the modes of angelic and human consciousness. We find here that two entirely different modes of subjectivities grounds these two different meanings of time. We in fact discover a personal grounding of time as experienced by different kinds of persons. Angelic persons have a different kind of time than human persons because of the kinds of persons of angelic nature versus human.
We can similarly apply this in regards to God. God is Three Persons in one substance. God does not in time or aeviternity, meaning that He does not experience time like man or the angels. God is outside of both time and aeviternity. He instead experiences eternity and eternity is described as an ever present with no past or future; it is a simultaneous whole. This means that the phenomenological differences between time, aeviternity, and eternity is ultimately grounded in personhood, in the kinds of personal beings God, man, and the angels are.
We can hence reply to those who claim that God must be a being within time simply by pointing out the fact that God is pure Act, and in order for God to exist in time, He then would not be pure Act. If God was in time then He must possess some potency since time is the measure of change. This further implies that God is a created being and not the Creator who creates out of nothing. When we think about the fact that all created being traces itself back to an uncreated Creator, it becomes self-contradictory to uphold the Catholic view of creation while admitting God is a being in time; for God is the Creator of time.
2.2.2. Time and Creation
Does time have a beginning or did it always exist? Similarly, did time exist before creation? Aristotle famously argued for the eternity of the world which necessitates the eternity of time. St. Augustine in City of God, on the other hand, argued that time indeed must have a beginning. If time is the measurement of change, then there must be something changing in order for there to be time. It makes no sense therefore to believe that time existed before creation, since this entails that something is changing when nothing existed since God had not yet created and He created from nothing. St. Augustine therefore concluded that time began with creation simultaneously.
St. Augustine gave a second argument for this view based on Scripture. The very first three words of the Bible are “In the beginning”. In order for there to be a beginning, there must be time. The beginning of time begins with the beginning of creation. God created nothing before “In the beginning”. St. Thomas likewise cites this same verse in support that time began with creation.
3. The Meaning of Time Travel
Contemporary discussions of time travel almost always use the concept of time and not eternity or aeviternity. It would in fact be meaningless to attempt to travel into eternity since such an endeavor is a metaphysical impossibility (as it would require one to become God). Time travel into aeviternity is impossible through time machines and spaceships simply because aeviternity is time as experienced by the angels. It is an immaterial, spiritual modality of time. It is essentially grounded in personal subjects, within the consciousness of the angels, though we do not mean to take such statements to the extreme of positing an idealist position of aeviternity. Time travel is hence restricted to those experiences of time within corporeal creation. We canfurther demarcate time travel to what is extrasubjective; for, in a broad sense, one could say that when a person reminiscences about the past that this is a kind of time travel though he and she remains in the present while subjectively dwelling or “reliving the past”. Such is not the object of our investigation.
To address the problem of time travel we must realize that there are in fact two kinds of time travel: travel into the past and travel into the future. Each is its own separate question.
3.1. Time Travel into the Past
The thought of time travel into the past is an obsession of our culture today. The movie Avengers: Endgame used it as a plot device to save humanity from Thanos. The notion is rather simple, use some kind of pseudoscience or pseudotechnology to travel into the past. A common theme of science fiction is that once someone does this, they must be careful to not taint the timeline or the sequence of events will be altered and hence generate a new temporal reality and a new history, such that the previous timeline is unknown and nonexistent except save for those who had altered it.
Such views introduce a principle of chaos into the universe. Nothing is set. All is in flux. Anything and everything can be changed and most people would not know any better. Reality becomes unreality because any time traveler can change everything by his or her mere breath. Is reality really that fragile? A consequence of this view is that one can go back and fix personal mistakes or prevent national atrocities. Likewise, one could promote tyranny and evil. It would only take a snap of one’s fingers to disrupt the entire stability of a current timeline and fundamentally alter its events. Such a worldview implies that time, and especially history, has no inner meaning or definite content. How can it when it can be changed at a whim, at the wish of anyone who possesses the technology? Reality becomes unreality because reality itself becomes meaningless. Time travel is fundamentally a radical skepticism about reality and its claims of lawfulness, order, and intelligibility. Laws of time certainly would continue to exist, just not matter, history, peoples and civilizations. The laws of matter collapse into laws of time, for matter itself is robbed of its coherence and is reduced to temporal being. All that remains are the half-dreamt fleeting glimmers of yesterday extinguished by the awakened dreamer and thence forgotten.
Such a view of reality is childish. It makes history beckon to the whim of the subject and his or her own whims. What one desires can be realized by changing time. Events are changed because one witnesses it and it’s accomplished by something usually trivial, like a push of a button or the snapping of one’s fingers. It is nothing other than to look at the world as if one were a child for only a childish perspective of reality can make one believe they can change the unchangeable through their own powers. It is a sign of immaturity in one’s intellectual life to believe such fantasies. It should come as no surprise that Endgame promotes such a childish view of reality given that the characters themselves refused to accept their own reality. The use of time travel plot devices almost always betrays a lack of creativity on the part of the producers.
3.1.1. The Problem of History
A more fundamental problem is analyzing the consequences the theory of time travel into the past poses as necessary corollaries for our theophilosophical understanding of history; that is to say, what does such a view require of us to hold for our theological and philosophical understanding of the phenomenon of history itself? To answer this question we must understand the importance of history for the Christian faith. Christianity is a religion, but what in part makes it distinct from other religions is its historicity. God became man to save man from himself. By becoming man, God entered time and human history. This is a definite historical datum that cannot be changed. The entire contents of Christian revelation is historical from Adam and Eve to the time of the Apostles and the early Church.
The Bible itself attests to historical truths. One in fact cannot reject the historical claims of the Bible for these truths fall under Scripture’s infallibility. Dei Verbum teaches:
Therefore, since everything asserted by the inspired authors or sacred writers must be held to be asserted by the Holy Spirit, it follows that the books of Scripture must be acknowledged as teaching solidly, faithfully and without error that truth which God wanted put into sacred writings for the sake of salvation.
This means that all truths, which includes historical truths, found in Scripture are asserted by the Holy Spirit, and since they are asserted by God, they are also infallible. There are some authors who attempt to water down this definition of inerrancy in Dei Verbum by arguing that infallibility only includes matters of faith and morals. This argument is based on a poor reading of the particular phrase from the quote above “for the sake of salvation” which they exegize as a restriction of inerrancy to only moral and theological truths. Such an interpretation is at odds with Dei Verbum and there are excellent refutations of this interpretation.
Dei Verbum further affirms that several books of the Bible are historical. The genre of some books are history, not fiction with mythic elements. The interpreter must pay attention to the genre of the individual books of the Bible in order to properly interpret them. Historical books must be treated as historical. Concerning the Gospels in particular the document teaches:
Holy Mother Church has firmly and with absolute constancy held, and continues to hold, that the four Gospels just named, whose historical character the Church unhesitatingly asserts, faithfully hand on what Jesus Christ, while living among men, really did and taught for their eternal salvation until the day He was taken up into heaven.
In sum, the historicity of the Gospels cannot be denied without denying the Christian faith. If the Gospels did not reliably pass on the historical truths of man’s encounter with God Incarnate, then the Catholic faith itself would be destroyed by a pernicious skepticism. Dei Verbum clearly rejects any historical skepticism of the Bible, and especially of the four Gospels.
One cannot accept the possibility of time travel into the past because history itself becomes meaningless, and likewise any religion that claims to be a historical faith. This follows because time travel into the past means that history can change. The fate of any timeline is in the hands of those who have the technology. History no longer has any definite truths to teach man about reality. History is stripped bare of its definite content for the voyeurisms of private whims. It does not matter that Adam and Eve fell if we can turn back time and stop the hand of Eve from reaching for the apple. Any sinful action can be undone through technology by traveling into the past. Even the Incarnation itself could be cancelled by the time traveler in principle. Such a conception undercuts the entire reality of the human drama as fallen beings who need God to save them, for man cannot save himself. Any belief in time travel makes man an idol of his own self.
Christianity has its own theophilosophical theory of time. Christians need to realize this. To be a Christian requires upholding that history is definite, irrevocable, linear and possesses intrinsic meaning. In the 5th century St. Augustine argued against another fallacious theory of time, the cyclical theory, and the criterion he used to demonstrate its falsity is what we used here, the truths of the faith. It is remarkable that it has been a constant task of Christianity to defend the essence and reality of history itself against those who attempt to delegitimize it and eliminate its meaning. Such attempts are the deviousness of Satan.
3.1.2. God and Time Travel into the Past
Up to this point we have given some considerations for why a Catholic, or Christian for that matter, should think twice about accepting the possibility of time travel into the past. Our investigation however has not yet delved into why time travel into the past is itself impossible. To dive deeper into the matter we must consider the consequences of accepting time travel into the past in lieu of who God is.
The Bible clearly teaches that God is immutable. The immutability of God means that God cannot change. Both the New and Old Testaments attest to this fact. In Malachi we read “For I the Lord do not change” and St. James writes “Every good endowment and every perfect gift is from above, coming down from the Father of lights with whom there is no variation or shadow due to change.” There are many other verses we could cite. We can also cite Dei Filius, God is “one, singular, completely simple and unchangeable spiritual substance.”
The immutability of God can be explained in terms of Aristotle’s act-potency distinction. St. Thomas argued for God’s immutability in this manner. Since God is pure Act without any potency, God cannot undergo change. If God cannot change, then He is immutable. It necessarily follows from this that God’s will is unchangeable. What God wills God cannot change. If God wills X, He cannot change His mind to will Y instead. “The counsel of the Lord stands for ever.”
The notion that one can time travel into the past fundamentally contradicts this dogma of the faith. If one were able to do such traveling, then God must necessarily change His will in order to allow for one timeline to be changed into another. What God wills in timeline A can change through time travel into the past such that timeline B arises, and since timeline B now exists, God must will it. Thus we discover that accepting time travel into the past necessitates that we contradict the faith concerning God’s immutability, from which it follows that God is not pure Act but possesses some potency of some kind. God would no longer be God. We therefore conclude that time travel into the past is impossible since it requires God to change His will, which is something He metaphysically cannot do. God cannot stop being God.
3.2. Time Travel into the Future
Time travel into the future is also a simple concept. One leaves his or her present time and enters some time into the future. Unlike time travel into the past, time travel into the future does not pose a problem concerning God’s will. One is not attempting to change God’s mind like traveling into the past, since one is going into the future, to events that have not yet occurred.
There is still a possible misinterpretation of time travel into the future. One can imagine time travel such as depicted in the movie Click where the protagonist used a remote control to fast forward through his life. One cannot fast forward through his or her life through a device. Regardless of what one is doing, time still proceeds at the same rate for that individual’s frame of reference. A view which allows one to fast forward through their life implies a form of perdurantism, which is to be rejected. Man cannot escape being a being in time. It is a vocation to authentically live out one’s own daily life.
Time travel into the future is possible according to Einstein’s theory of relativity with the phenomenon of time dilation when one travels at relativistic speeds. A common explanation of this is the twin paradox. If two twins are born, one, twin A, stays on Earth his whole life while the other, twin B, is placed in a spaceship traveling at relativistic speed. Twin B travels on the ship for one year and returns to Earth one year later in his life. When twin B meets twin A, twin B discovers that twin A aged 30 years in comparison to his one year of aging. Twin B experienced time at the same rate according to his frame of reference, the same as twin A, but because twin B traveled at relativistic speed the rate time actually changes is decreased in respect to twin A’s frame of reference.
Part of the revolutionary perspective Einstein introduced with his theory of relativity was considering time as a dependent variable of velocity. The rate of change for time depends on one’s velocity. The time dilation equation has the rate of change for time as a variable dependent upon the ratio of the velocity of the traveler to the speed of light. The traveler at relativistic speed still experiences time in the same way as someone on Earth, but time passes at a faster rate for the Earth bound observer.
The time dilation phenomenon can be experienced on Earth. If one flew in a commercial airliner around the Earth, his or her clock would be one second off from the rest of the world. Scientists took two identical clocks and placed one at the top of a water tower and left the other on the ground beside it. They discovered that when they brought the clock from on top down that it had a different time. A similar experiment can be performed by traveling up a mountain.
Einstein introduced a revolution in how man understands time. Before him time was considered as something absolute, proceeding at the same rate everywhere in the galaxy. Today, the common understanding is that time is relative. Time is relative in that it is dependent upon the traveling object’s velocity in order to determine its rate of change. Time is experienced at different rates by different astral objects because each themselves are traveling at different speeds. When the physicist declares that time is relative, this is not to imply that time does not exist, but only that it is dependent on the traveling object’s velocity.
It is possible some day that scientists and engineers create some type of spaceship such that when the ship leaves Earth traveling at a relativistic speed and returns to Earth a short time later, that the travelers discover the Earth to be 2,000 years older. Whether such a feat is possible appears to be a question reserved for the physicist. I at least do not see a feasible theological objection to time travel in the future at present.
One possible theological objection to time travel in the future is Jesus’ Second Coming at the end of the world. It would seem that one cannot travel at relativistic speeds since then he or she could possibly miss the apocalypse. Such an argument is however rather poor given that it presupposes an earth-centric view of the apocalyptic event which need not be the case. Jesus could inaugurate his Second Coming all the same and take into account those who are traveling at relativistic speed. The apocalypse, properly speaking, is not strictly an Earth event, but cosmological. The entirety of the cosmos will be affected radically when Jesus returns:
But the day of the Lord will come like a thief, and then the heavens will pass away with a loud noise, and the elements will be dissolved with fire, and the earth and everything that is done on it will be disclosed.
Considering our analysis and what is commonly depicted in science fiction about time travel, it should be apparent that most films and television shows demonstrate the vain speculations man easily entraps himself with. Time travel has its paradoxes, like the twin paradox, but we must be on our guard to not give into frivolous speculations that can only damage one’s intellectual life. We must remind ourselves of Victor Hugo’s insight that those “who reads stupidities is not without impunity.” We can add to this watching stupidities will likewise leave its mark.
 On the Heavens, Bk 1, ch 9.
 College Physics, OpenStax, p. 36.
 ST 1, Q10, A5, ad 3.
 Handbook of Catholic Apologetics, 99.
 See Seifert’s Back to the Things Themselves on the many meanings of objectivity.
 Cf. Heidegger’s Being and Time. Hartmann’s New Ways of Ontology.
 One example is Richard Swinburne.
 ST 1, Q10, A4, A5.
 ST 1, Q10, A1, A2.
 City of God, Bk 11, Ch 6.
 ST 1, Q46, A3.
 This however does not imply that all the books of the Bible are historical. Genesis 1-3 in particular uses mythic poetry to convey historical truths such as God created and all men descend from Adam and Eve. A mythopoetic hermeneutic of man’s prehistory however does not necessitate the acceptance of the view that God literally created in six days.
 DV 11.
 See Scott Hahn's "For the Sake of Our Salvation" in Letter and Spirit, vol 6.
 DV 12.
 DV 19.
 City of God, Bk 12, ch 14
 Malachi 3:6.
 James 1:17.
 Ps 33:11; 102:25-27; Is 46:8-10; Heb 6:17.
 Dei Filius 1.2.
 ST 1, Q9, A1, see also A2.
 ST 1, Q19, A7.
 Ps 33:11. Cf. Heb 6:17.
 See Prov 31:10-31.
 A famous depiction of this is the original Planet of the Apes movie.
 2 Pt 3:10
 Les Miserables.
Wanderer above the Sea of Fog by Caspar David Friedrich