Open a recent companion to (or handbook of) metaphysics and it is highly unlikely that you will find in them any discussion of the notion of eternity. It is not only that eternity does not figure as one of the subjects of the main articles in these books, but even the index at the back of the volume may hardly make any mention of it.
For the most part, we relegate the concept of eternity to the apparently less rigorous – and somewhat less respected – field of philosophy of religion, or even theology. We associate eternity with the promise of an afterlife, and just as the resurrection of the dead and other miracles do not figure in current discussions of metaphysics, so it seems that serious metaphysics should stay away from the shady ghost of eternity.
But why, precisely, is this so? That is, what brought eternity into such philosophical disrepute? True, the term “eternity” (and its cognates in many European languages) is somewhat equivocal. In some cases, “eternity” denotes existence in all times, or omnitemporality; in others, existence that is not in time at all. These two senses of “eternity” are clearly distinct, yet it is highly unlikely that this systematic equivocality of the term throughout the history of Western philosophy is the reason for its current unpopularity. For consider two philosophical terms that are currently in vogue: “part” and “consciousness”. Both terms are far more polysemous than “eternity” (each should have at least half a dozen distinct meanings), and yet we are hardly afraid of the task of engaging in the study of mereology or consciousness. We simply do our very best to keep the possible ambiguities in mind and avoid confusing the various senses of the terms. “Part” and “consciousness” are terms that are so crucial for understanding our world that we simply cannot afford to dispense with them. But is not “eternity” a term of the very same class?
As the volume I have recently edited – Eternity: A History, Oxford University Press, 2016 – illustrates, the two distinct concepts of eternity are ubiquitous in Western (and non-Western) culture, literature, art, and even music (yes music: just stop and think for a moment about how a composer might succeed in representing atemportal eternity, when music, by its very nature, is a temporal art).
Moreover, the notion of existence that is not in time is not that odd. (Think of numbers. If you believe that the square root of two – unlike the largest prime number – exists, and that the square root of two is not getting older every millisecond, then there is quite a good chance you will find yourself committed to non-temporal existence). But even if you are not moved by Mc-Taggart’s arguments for the unreality of time, or by the arguments of some branches of current speculative philosophy of physics which suggest that space-time is grounded in a more fundamental layer of reality, it remains true that conducting thought experiments about how a timeless world would look is not only fun, but may well result in genuine insights into fundamental reality.
It would be hard, perhaps impossible, to write a novella in the style of Edwin Abbott’s Flatland (1884), but with characters that are atemporal, instead of two-dimensional. “It is impossible to write a story of this kind since nothing – literally nothing – happens in it! At most, you might have a depiction of a frozen state of affairs or a painting” – you would say. But wait — even if nothing happens in the story, there may still be characters. Both a rock and a mind might be “frozen” in time, but this alone does not eliminate the difference between the animated and the non-animated. A timeless mind would have no past memories or future hopes, but it may still have wishes (“I wish I were there rather than here”, “I wish I knew everything”, or even, “I wish I were next to you”). The mental life of a timeless mind would be radically different from anything we know, yet it is not obvious that mentality without time is just a contradiction in terms. Indeed, on second thought, it is not even clear that we could not have a story about timeless entities.
Here is the blueprint for a timeless translation of a famous narrative with which you are surely familiar. R and J wish to be (in a world in which they are) next to each other (in fact they wish to be next to each other in all possible worlds!). Alas, R and J belong to the groups of M and C (respectively) and the vast majority of members in each group wish to make the other group nonexistent, or at least, far away from themselves (in fact, each group wishes to be away from the other group in all possible worlds). Poor R and J face an impossible situation. Their desires must be unrealised as long as they remain members of their groups (i.e., as long as R and J are members of M and C in all the worlds in which they are instantiated). In short, they are tragic figures.
Now, you may well respond to the above narrative by pointing out how simple and pale our narrative is in comparison with Shakespeare’s Romeo & Juliet. Point taken. Still, a novelist or playwright (neither of which do I pretend to be) should use her imagination in order to compensate for some restrictions on her literary devices by developing other features which we commonly neglect. Thus, we can perhaps imagine a timeless adaptation of Romeo & Juliet in which temporal locations and relations are systematically replaced by locations and relations among members of distinct possible worlds (while restricting our possible worlds merely to timeless ones).
Thought experiments with eternity may help us uncover the logic of this concept. But thought experiments are not the only philosophically profitable way of approaching this old yet improperly studied notion (or pair of notions). Here is a quick and almost random list of eternity-related questions and problems I find exciting (some of which have hardly been broached in the two and a half millennia of engagement with the notion of eternity in Western philosophy). The common element to the atemporal and omnitemporal concepts of eternity is that eternity seems to be the most robust kind of existence (for this reason it was commonly assigned to God in many theological traditions). But why precisely is eternity more real than temporal existence? Furthermore, what kinds of relations, if any, might obtain between eternity (or eternal entities) and time (or temporal entities)? (Are these causal relations? If so, what kind of causality do we have in mind?) Are there any explanatory relations between eternity and time? If so, are these explanatory relations symmetric or asymmetric?).
Atemporal eternity raises a cluster of more specific questions. For example, what is the relation between timeless eternity and the present tense? (Both have no temporal extension, yet still they seem to be distinct: the one is followed/preceded by other tenses, the other is not. Still, can we point out an intrinsic characteristic of the present which distinguish it from atemporal eternity?) Another intriguing question about timeless eternity – this time at the centre of a long history of debate – is whether the notion of atemporal action is intelligible? And if we can make sense of the notion of atemporal action, could we also consistently conceive of life that is atemporally eternal?
Perhaps even more basic is the question of what kinds of things may be (or are) eternal? Can nonexistent things – such as flying hippos or square circles – be eternal? (Notice that square circles are similar to numbers in that they do not undergo change. Should we count square circles as eternal if we grant eternity to numbers?) And how about quotidian material things. Clearly, most tables do not last forever, nor do we normally conceive of a table as existing outside of time. Still, is there something inherent in the nature of material things that makes them essentially non-eternal (in either of our two senses of “eternal”)?
We have so far discussed the two distinct senses of “eternity” that we find in Western philosophy and in many European languages. Obviously, it merely is an interesting accident that in certain languages a term has two distinct meanings. In other languages, there are distinct terms for existence in all times and atemporal existence respectively. Moreover, it is also not completely precise that throughout the history of Western philosophy we find only two main senses for “eternity”. If we look closely at the work of Benedict de Spinoza, the great metaphysician of modern philosophy, we encounter an understanding of eternity that is distinct from both omnitemporal existence and atemporality.
In fact, for Spinoza, eternity has very little to do with time at all. Rather than being a certain kind of temporality, for Spinoza eternity is truly just a modal notion: it is existence which is self-necessitated, i.e., existence which is grounded in the very nature or essence of a thing. Such existence cannot come into or out of being. The intimate connection Spinoza establishes between eternity and (self-)necessity opens up a whole new horizon of theoretical possibilities. Could we have a modal logic of eternity? Could we make sense of iterations of the eternal predicate and speak of “eternal depth”, i.e., would being eternally eternal be any different from being simply eternal? Furthermore, since Spinoza distinguishes between self-necessitation (i.e., eternity), and necessitation-by-another, what kind of relations may obtain between things belonging to these opposite kinds of necessary being?
Metaphysics as an independent discipline has a surprisingly short history. Until the early eighteenth century, many, perhaps even most, writers on “metaphysics” primarily had the eponymous work of Aristotle in mind. In the writings of the early eighteenth-century German rationalists – Christian Wolff and Alexander Baumgarten – we find a conception of metaphysics that is no longer tied to Aristotle’s great work. But metaphysics as a discipline was not blessed with longevity, as a dozen years or so before Louis XVI it was condemned to the guillotine by Kant’s first critique. The fate of metaphysics after the Kantian revolution is a story that still needs to be told, but it would be fair to say, I think, that for the past two centuries engagement with heavy metaphysical concepts such as eternity has been taken to be either a form of backwardness (religious or otherwise) or a kind of eccentricity.
Luckily, things seem to have changed somewhat over the past twenty years. Suddenly, for example, we are seeing debates about monism appear in mainstream journals. (This could hardly be imagined in the 1970s or 1980s.) The emergence of interest in metaphysical monism as well as the persistent engagement with the philosophy of modality may open a window of opportunity through which eternity could again take her rightful seat as a fundamental notion of metaphysics.