Before beginning to look at time and eternity it is necessary to ask two questions; what is time and what is eternity? Eternity is most often thought of as existence for a limitless amount of time although many use it to mean a timeless existence altogether, an existence outside of time itself. So our concept of eternity is in many ways dependant on our concept of time. So then what is time? This has been discussed and pondered by many philosophers beginning with Aristotle, who speculated that time may be motion. He did however add that motion could be slower or faster but time could not be, it was a constant. Aristotle obviously did not know about Einstein’s theory of relativity in which time can also change. Also when Einstein was working on his theory of general relativity and proposed his then revolutionary idea that mass can curve space, he was not aware that the universe was expanding. So our concept or definition of time is still something which, with our further discoveries of how the Universe is constructed, we are still developing. So we will then take a look at how time and eternity have been viewed historically by philosophers and how this has been developed up to the present day. Let us first take a look at the progression of our concept of time.
In ancient Greek philosophy Plato speaks about the Demiurge. The demiurge is a term for an artisan-like figure which is responsible for the fashioning and maintenance of the physical universe. The demiurge however is not the creator figure in the monotheistic religious sense, both the demiurge itself and the material from which the demiurge fashions the universe are considered either uncreated and eternal, or the product of some other being. Plato speculates that the Demiurge creates order in the universe. The Demiurge is a force that provides order and stability of a kind and has an important place in Plato’s thought on time. In the Timaeus, several possible arguments can be chosen concerning the nature, beginning or indeed no beginning of time.
Aristotle in contrast to Plato tries to prove in his Physics, that time neither has a beginning nor an end. His main argument revolves around the point that time or motion always was. If something that had the qualities of motion of movement existed, then it would either have to have been in constant movement or begun to move. Therefore, something that begins must too end. “That the heaven as a whole neither came into being nor admits of destruction, as some assert, but is one and eternal, with no end or beginning of its total duration, containing and embracing in itself the infinity of time, we may convince ourselves not only by the arguments already set forth but also by a consideration of the views of those who differ from us in providing for its generation.”  For Aristotle time can have no beginning or end. Something which begins cannot continue on for eternity. His thought also applies to ideas such as the beginning of the world, since for the world to change, or begin, God or the Creator would have to be subject to a god changing his mind but this would be impossible. Simply put the idea of their being a beginning to time is contrary to Aristotle’s thought.
If we go back to Augustine, we see the importance of Scripture in the Confessions. Therefore in relation to time, if we take the following passage from the Book of Genesis, then we shall see the basic workings or the initial starting point for Augustine’s theory on time. In the beginning God created the heavens and the earth. Now the earth was formless and empty, darkness was over the surface of the deep, and the Spirit of God was hovering over the waters. And God said, ‘Let there be light,’ and there was light.” 
It is clear that ‘in the beginning’ there must have been a first step taken for the world and indeed the universe to come into existence, and this was the will of God. Augustine begins Book XI by asking “O Lord, since eternity is Yours, are You ignorant of the things which I say unto You? Or see Thou at the time that which comes to pass in time? Why, therefore, do I place before You so many relations of things?”  Augustine appears to be afraid that God is somehow frozen in Eternity, truly without change, without any role to play. However, he does take comfort in the hope that “we also pray, and yet Truth says, ‘Your Father knows what things you have need of before you ask Him.’ (Matt 6:8)”  So God will provide for Augustine, or at least he hopes and believes having red scripture that God provides for him. So too has God given us the world and the universe. That he has created all of these things is enough for Augustine, as he says in Chap. 4 of book XI “They [the heavens and the earth] also proclaim that they made not themselves; therefore we are, because we have been made; we were not therefore before we were, so that we could have made ourselves.”  Here we see Augustine marvel at God in his creation of the universe. For Augustine he is trying to show how time came into existence with the creation of Heaven and Earth. God created this universe and everything in it and time, as we know it, began with creation, ‘In the beginning’.
Yet there are some questions that need to be answered as St. Augustine shows us. “And no times are co-eternal with You, because You remain for ever; but should these continue, they would not be times. For what is time? Who can easily and briefly explain it? Who even in thought can comprehend it, even to the pronouncing of a word concerning it? But what in speaking do we refer to more familiarly and knowingly than time? And certainly we understand when we speak of it; we understand also when we hear it spoken of by another. What, then, is time?”  This is a very good question, but is there an answer? Augustine does not seem to be able to find one. When he comments on people who ask what God was doing before time began he says “Behold, I answer to him who asks, What was God doing before He made heaven and earth? I answer not, as a certain person is reported to have done facetiously (avoiding the pressure of the question), He was preparing hell, says he, for those who pry into mysteries… I boldly say, That before God made heaven and earth, He made not anything. For if He did, what did He make unless the creature? And would that I knew whatever I desire to know to my advantage, as I know that no creature was made before any creature was made.” 
Augustine does try to explain eternity being a moment of time, “But should the present be always present, and should it not pass into time past, time truly it could not be, but eternity.”  Time then, as opposed to eternity, is always moving and it is always in motion, as Aristotle said. Eternity, however, remains constant, unchanging and complete. But still we are left with that seemingly simple question; what is time?
If we look at time as motion, constantly moving on, then we can look at past time or uture time. It is difficult to try and make any concrete claims over the issue of past, present and future. For example, if we say that the past day has been a long one, are we not talking about a day or a state that no longer exists? This is also the case if we speak about the future. How can we comment on the future, e.g. it will be a cold week or a warm day, if it does not exist. But can we measure time in the present? Augustine launches into discussion of the present time that shows the futility to grasp what time is. “But we measure times passing when we measure them by perceiving them; but past times, which now are not, or future times, which as yet are not, who can measure them? Unless, perchance, any one will dare to say, that that can be measured which is not. When, therefore, time is passing, it can be perceived and measured; but when it has passed, it cannot, since it is not.”  Augustine continues to narrow down the present time into days, hours, moments, heartbeats and eventually into a single moment, “If any portion of time be conceived which cannot now be divided into even the minutest particles of moments, this only is that which may be called present; which, however, flies so rapidly from future to past, that it cannot be extended by any delay. For if it be extended, it is divided into the past and future; but the present has no space.”  We have come to a stage whereby it is almost pointless trying to even understand time, whether past, present or future.
Augustine’s discussion on time is impressive but he is faced with that question again, that still has not been answered. What is time? It is too difficult, perhaps impossible, to offer plausible explanations. “The answer to the question of time is to be found, paradoxically, outside of time.. in eternity” We exist in this temporal world, but do not understand fully what time is to us. We are simply not in a position to fully comprehend time. After much searching, debating and discussing, Saint Augustine slowly winds down to a prayer, a prayer of acceptance and hope. “You unchangeably eternal, that is, the truly eternal Creator of minds. As, then, Thou in the Beginning knew the heaven and the earth without any change of Your knowledge, so in the Beginning Thou made heaven and earth without any distraction of Your action. Let him who understands confess unto You; and let him who understands not, confess unto You. Oh, how exalted are You, and yet the humble in heart are Your dwelling-place; for Thou raisest up those that are bowed down, and they whose exaltation You are fall not.” 
God exists outside of Time. Time is a creature created by God. God’s Will is not temporal like our own. That Eternal God exists allows for everything we know. So, we ask again, what is time? According to Augustine, and other Christian writers and thinkers, It is a creation, just like you or me. We exist in it and travel in this temporal world, universe towards something. What that something is, in Christianity anyway, is eternity. So then we now ask ourselves the question, what is eternity?
Concepts of eternity have developed along with the development of the concept of God in a Western context. Eternity has been viewed in history both as timelessness and as everlastingness and following the work of Boethius and St. Augustine divine timelessness became the dominant view. The two views were however very different. “Boethius presented the idea of divine eternity as straightforward and relatively problem-free, while Augustine wrestled with the idea and expresses continual puzzlement and indeed amazement at the idea of time itself and with it the contrasting idea of divine eternality.”  We have already looked at Augustine’s struggles with what time is, but what does Boethius say?
“It is the common judgement, then, of all creatures that live by reason that God is eternal. So let us consider the nature of eternity, for this will make clear to us both the nature of God and his manner of knowing. Eternity, then, is the complete, simultaneous and perfect possession of everlasting life; this will be clear from a comparison with creatures that exist in timeaˆ¦ for it is one thing to progress like the world in Plato’s theory through everlasting life, and another thing to have embraced the whole of everlasting life in one simultaneous present.” 
Boethius asks the questions about eternity in regard to providence, how can God know about something before it happens, but not then control or influence the free will which he gave to human beings?
His answer is to do with the mind of God. God does not know the world in the same way that human beings do because God exists outside of time, so he doesn’t view the world as a progression of events. He does not see past present and future as we might but at the same time he knows all future acts and remembers all past acts. He sees the world in one single act, which includes knowledge of every choice of every human being from the beginning of the world to the end. Therefore he doesn’t influence the free will or choices of human beings but he did, and indeed does, already know them.
In metaphysical terms eternity could be summed up by asking the question can anything be said to exist outside of time and space and if it can how can it and, maybe more importantly, why?
Many religions say that God is eternally existent but how we understand this depends on which definition of eternity we use. God might exist in eternity which means a timeless existence where the past, present, and future just do not mean anything. On the other hand, God might exist for eternity, which means he has already existed for an infinite amount of time and will continue to exist for an infinite amount of time. There is another definition that states that God exists outside the human concept of time, but also inside of time because if God did not exist both outside and inside time he would not be able to interact with humans as he does through answering prayers etc.
Whichever definition of eternity we use it is safe to say that humans cannot fully understand eternity, since it is either an infinite amount of time or something other than the time and space we know. If we use the concept of God as Creator, as a being completely independent of “everything else” that exists because God created everything else. If this premise is true, then it follows that God is independent of both space and time, since these are properties of the universe. So then, according to this notion, God existed before time even began, he exists during all moments in time, and he will continue to exist after the universe and time itself will cease to exist.
St. Thomas Aquinas in his Summae Theoligica argues against Boethius’ concept of time and eternity, he says “As we attain to the knowledge of simple things by way of compound things, so must we reach to the knowledge of eternity by means of time, which is nothing but the numbering of movement by ‘before’ and ‘after.’ For since succession occurs in every movement, and one part comes after another, the fact that we reckon before and after in movement, makes us apprehend time, which is nothing else but the measure of before and after in movement. Now in a thing bereft of movement, which is always the same, there is no before or after. As therefore the idea of time consists in the numbering of before and after in movement; so likewise in the apprehension of the uniformity of what is outside of movement, consists the idea of eternity.”  He is saying that what is eternal is interminable, that it has no beginning nor end and that because eternity has no succession like time, moment after moment in past present and future, it is therefore ‘simultaneously whole’.
He says also that “The idea of eternity follows immutability, as the idea of time follows movement, as appears from the preceding article. Hence, as God is supremely immutable, it supremely belongs to Him to be eternal. Nor is He eternal only; but He is His own eternity; whereas, no other being is its own duration, as no other is its own being. Now God is His own uniform being; and hence as He is His own essence, so He is His own eternity.” Is it therefore the case that when we speak of eternity we speak of God? Is God the only thing that can be eternal? Certainly it is true that scientifically the only things we can know are those we experience in life but eternity, although almost universally accepted as a fact, is unknowable to us at least in our lifetimes. When we go, as Christians and others believe, to eternal life after this life, then we may have knowledge of eternity as we have experience of it with God as he is, but here and now we can ask what is eternity but we can never really answer it.
According to William Lane Craig, “on a relational view of time God would exist timelessly and independently ‘prior’ to creation; at creation, which he has willed from eternity to appear temporally, time begins, and God subjects himself to time by being related to changing things. On the other hand, the Newtonian would say God exists in absolute time changelessly and independently prior to creation and that creation simply marks the first event in time.”  According to the Christian doctrine, still taught to this day, of creatio ex nihilo, the universe began to exist a finite amount of time ago. And this doctrine, according to Craig, ‘receives philosophical confirmation from arguments demonstrating the absurdity of an infinite temporal regress of events and empirical confirmation from the evidence for the so-called ‘big-bang’ model of the universe.’  But while we might agree that the universe began to exist, does this also mean a beginning to time? If one believes that time exists separately from events in the sense that if there were no events there would still be time, then there need not be a beginning to time as it exists outside of events. To say that the universe began to exist on such a time scale would simply be to say that a finite time ago there were no physical objects. However if one accepts that time cannot exist apart from events, then this means that the beginning of events, or beginning of the universe, would also be a beginning of time. So then is eternity simply a never ending period of time? Or does it exist separately and independently of time? We might ask in regard to God what does it mean to say that God is eternal? It can mean that he exists in divine timelessness or in divine temporality.
Divine timelessness is the traditional view of God as being outside of time. It is the position advocated by Augustine, Boethius and Aquinas who we have looked at and also others such as St. Anselm.
Divine temporality also holds the notion that God is omniscient and omnipotent. It is important to say that God’s temporality is not to be interpreted as a limit to his power, knowledge or being. Those who uphold a divine temporality view have problems with the views of the divine timelessness of God and indeed it has recently come under criticism by some philosophers and also by some theologians.
Oscar Cullmann, a theologian, wrote that “Primitive Christianity knows nothing of a timeless God. The ‘eternal’ God is he who was in the beginning, is now and will be in all the future, ‘who is, who was, and who will be’ (Rev 1:4). Accordingly, his eternity can and must be expresses in this ‘naive’ way, in terms of endless time.” 
Richard Swinburne, a philosopher, wrote that “the claim that God is timeless … seems to contain an inner incoherence and also to be incompatible with most things which theists ever wish to say about God.”  In this view God’s eternalness is expressed as being everlasting, without beginning and end, but he experiences time and is therefore able to work within time, and so is involved and working in time with us.
This divine temporality is indeed a modern Christian view. It has often been stated in sermons around Christmas time that the birth of Jesus, the incarnation, God becoming man, signalled God entering into time and space with us and he continues to be with us in that same way. John M. Frame states that “On Christmas, we celebrate something quite wonderful: God entering our time and space. The eternal becomes temporal; the infinite becomes finite; the Word that created all things becomes flesh.”  He does also note a paradox though in this notion of God entering Space and time by saying “From day to day, from hour to hour, the changeless God endures change. But God the Son incarnate is still God, still transcendent. As he responds to events in time, he also looks down on the world from above time and space, ruling all the events of nature and history.”  So why enter time at all? The Christian answer is that he did this to show us how much he loves us, by dying for us, in our place, so that we might have eternal life. Even now God is both God and man, forever, so that he doesn’t just rule is from above, but walks with us in every step, in every experience of our lives. As Frame puts it; “So Christmas reveals in a wonderful way that God acts in time as well as above it. It shows us wonderfully how God relates to us, not only as a mysterious being from another realm, but as a person in our own time and place: interacting with us, hearing our prayers, guiding us step by step, chastising us with fatherly discipline, comforting us with the wonderful promises of the blessings of Christ. Truly he is Immanuel, the God who is really with us, who is nonetheless eternally the sovereign Lord of all.” 
Taking Christ as a pointer to God in both eternity and in time we see in John’s Gospel Jesus say of himself “Before Abraham was, I am” (John 8:58). With the use of two different tenses, past in reference to Abraham and present in terms of Christ even though logically it should be past tense we are given an insight maybe into what eternity is, separate to time, at least as we know and understand it.
Arthur C. Custance says in his book ‘Time and Eternity’ that “The really important thing to notice is that time stands in the same relation to eternity, in one sense, as a large number does to infinity. There is a sense in which infinity includes a very large number, yet it is quite fundamentally different and independent of it. And by analogy, eternity includes time and yet is fundamentally something other. The reduction of time until it gets smaller and smaller is still not eternity; nor do we reach eternity by an extension of time to great length. There is no direct pathway between time and eternity: they are different categories of experiences.”  Therefore we experience time and cannot have a full understanding of eternity due to the fact it is beyond any experience we can have. So then why even ask about it, or even entertain the thought of it?
Christoph and Johann Blumhardt in their book “Now is Eternity” give our reasons for asking about ternity quite simply when they say that “The deepest need each of us has, even if we are not conscious of it, is that of eternal life.” 
In the book they discuss the impact that the loss of any awareness of eternity has had on the modern world. They say that for most people in today’s world it is the temporal and transitory things of life that are most important for them. This is because these things are immediate, tangible, and visible. But it means that the eternal dimension of life – that part of it that is divine and thus enduring – is never acknowledged or sometimes never even realised that it is there.
They go on to say that “When eternity is forgotten, human destiny is robbed of its real significance, and the goal of life limited to the search for fulfilment on an earthly plane. Remembered, it enlarges our view and, through what is best and noblest in us, reminds us of the promise of another home on a higher plane: the world from which we come, and to which we must one day return. To be mindful of eternity is to know that our earthly existence will one day be overshadowed by the eternal reality of everlasting life.”  Eternity is a part of who we are just as much as time is. We may live in time now but when we die we go to eternity, it is as much of what makes us human than anything else and therefore as we are destined for eternity we have that innate yearning and calling to know it and understand it, as with every other aspect of our being, but never will until we can experience it. When we read Augustine’s wonder and amazement when he is pondering time it is something quite remarkable. It shows a man who has genuinely tried to walk the path of enlightenment. Augustine was faced with some problematic questions that were unanswerable, at least by the human mind and condition. Time is a creature that is so real in our lives, but is as fleeting as the wind, we cannot truly grasp it. Searching for time in the past, present, and future Augustine finds that it is a fruitless act. The answer to the nature of time is to be found in Eternity. That something so great, with a life span that has stretched from the beginning is a creature willed into existence by the Eternal God. That God is, guarantees our existence. God provides for Time and for Creation by His existence. We move also then to talk of eternity, if the nature of time is to be found in Eternity then we must ask what is eternity? The answer to this question then is again impossible to grasp, but the best clues to it’s answer are found in scripture. In the Old Testament God is referred to in the present, ‘I am’, not I was or I will be but ‘I am’. This eternal state of being constantly in the present is our greatest insight into what eternity is.
After wrestling with all these thoughts of time and eternity and what they are or, more accurately as we cannot fully grasp the concepts, what they might be, we are left back with Augustine and his ultimate belief that the mysteries in which he engaged only turn us towards something greater, something final, and that something is God. Ultimately the path to eternity, that is God, requires not an enlightened mind but a ready faith. We can ask all the questions we want, but in the end we must wait until we are with God, because at it says in the Eucharitic prayer at Mass “On that day we shall see you, our God, as you are”.  And then we shall grasp the concept of not only eternity but time and every other thing that we could not grasp here on earth, coming to true knowledge of God and therefore full knowledge of the Truth.