The aim of this book is twofold: in the first part, it is to propose a new solution to the problem of how relativity theory relates to the passage of time ; in the second part, it is to spell out, in the light of this solution, the relationship between divine eternity, change, and time.
The issue of the first part of the book is one which the philosophy of time has been grappling with for over a century: On the one hand, time appears to be fundamentally asymmetric in character, being marked by a unidirectional flow from a fixed and irretrievable past towards a future which is open and can be influenced. Moreover, there is an overwhelming impression that past, present and future events differ fundamentally in their ontological status. On the other hand, strong arguments deriving from physics, especially relativity theory, speak against the above common-sense view of time. In particular, the notion that there is such a thing as a state of the universe at a certain time, and hence also a present state of the universe which separates its past from its future, are strongly called into question, so that past, present, and future events must be given the same ontological status. This point is reinforced by philosophical arguments which show the notion of a passage of time to be deeply problematic and even aporetic.
A further crucial datum which philosophy of time must take into account in this context is the fact that contemporary science describes a universe which undergoes a development from earlier to later stages, marked by different physical characteristics, from the big bang to the stage we are living in. Yet how is such an evolutionary cosmology possible if there is no such thing as the universe at a certain time?1
Philosophy of time therefore faces the task of āsaving the phenomenaā and accounting for why time seems as it does, and furthermore of assessing whether and how a truly evolutionary cosmology is possible, given the strength of the arguments against a common-sense view of time. Although much has been written on this subject, philosophy is still struggling with it. In my view, there is a too strong polarization between two opposing views, with still little on offer by way of a third alternative: On the one hand, there is the block universe model, whereby the abolition of a global past-present-future distinction results in a universe in which all events are in a certain sense already there and whose history is āwrittenā and laid down, whereas our intuitive view of a flowing time, and our impression that the future contains several possibilities, is illusory, a position which has also become known as eternalism. On the other, the defenders of the intuitive view of time, known as A-theorists, have by and large subscribed to an absolute passage of time, with a global moving ānowā and an associated past-present-future distinction valid for the entire universe, believing this to be necessary for there to be true becoming and a genuinely evolving world, and often positing quite implausible physics in order to make such a model possible.
To do justice to a changing and evolving world which, as I believe is convincingly shown by relativity theory, lacks a global past-present-future distinction, a new model is needed. The one developed in this book draws on arguments and insights coming from both physics and philosophy. Crucially, it is made possible by a theory whereby time is due to change in things, so that time is not itself a thing, or substance, existing in its own right. In particular, time is not thought of as a succession of instants, or ānowsā, independent of change occurring in the world. I will therefore make much use of Aristotelian and scholastic theory of time which, in my view, has a lot to offer for the task of spelling out the relationship between change and time, as well as insights from set theory and mathematical analysis.
Such a model, as I will argue, is up to the task of explaining phenomena such as timeās one-way street character and the fact that agents can influence their future, but not their past. It furthermore allows for true becoming, and in combination with results from general relativity theory, it also makes a genuinely evolutionary cosmology possible. However, the theory proposed here is not an A-theory: it does without a global tide of becoming and without the notion that events change their ontological status by flowing from the future via the present into the past. Rather, all really occurring events, considered in themselves, have the same ontological status.
The model proposed in this book builds upon much groundwork in both physics and philosophy which must be considered first. Chapter 2 provides an overview of the available models of time concerning questions such as the following: Is time a thing, or substance, in its own right? Is there a true passage of time and an associated distinction between past, present, and future, or must this common-sense view of time, as many have argued, be rejected as illusory? The chapter places particular focus on the temporal ordering of events, and its final section is devoted to the notions of the instant moment and that of the universe at a given time.
Special relativity theory has decisively influenced the philosophy of time. Chapter 3 therefore discusses, first, the immediate consequences of this theory: the loss of absolute simultaneity, but also the invariant temporal order of causally connectable events. Next, the arguments advanced by Wim Rietdijk and Hilary Putnam in favour of universal determinism which, as they claim, results from relativity of simultaneity, is discussed, as well as the critique of this argument. It will also emerge that proposals for locating an observer-independently significant past-present-future distinction in Minkowski spacetime lack credibility. The chapter closes with a point of philosophical importance emphasized by Hans Reichenbach: the structure of world lines and light cones in relativity only works for relatively large, composite objects, and breaks down at the quantum level.
Contemporary evolutionary cosmology describes a universe whose different overall properties change with its age, a finding which seems to contrast with the upshot from Chap. 3 and to restore the notion of the universe at a given time. As will be argued in Chap. 4, accounts of the development of the universe with time can be given in a unique way by using the so-called cosmic time functions which can be defined in general relativity theory, given that we inhabit a homogenous and isotropic universe. After introducing cosmic time and its role in cosmology, I will explore its scope and limits. It will become clear that cosmic time does not save a global past-present-future distinction or a total temporal ordering of all events. The final section of Chap. 4 assesses the argument whereby quantum mechanics establishes an absolute, observer-independent simultaneity between events, and hence also a true ānowā. We will see, however, that this argument backfires.
The apparent contrast between the obviously asymmetric characteristics of time and the results of spacetime physics has generated a substantial body of literature addressing this problem. Chapter 5 gives an overview and assessment of anāobviously not exhaustiveāchoice of relevant works. It illustrates the polarization between the two opposing camps mentioned above, but also introduces the work of some authors who have proposed a third way, arguing for true becoming, while rejecting the global advancing ānowā.
This latter concept, as I argue in Chap. 6, does not help us to construct a physically and philosophically plausible model of time: the global moving ānowā not only conflicts with relativity theory, but also it has no causal role, explains nothing, and only creates needless philosophical problems. Nor, as will be seen, are irreversible processes in physics good candidates for explaining the one-way street character of time.
Chapter 7 argues that the way forward to meet the challenge stated initially lies in a theory which understands time as based on causal interactions between substances, one which entirely dispenses with the global moving ānowā. In order to develop such a theory, I first consider aspects of Aristotelian and scholastic thought on the topics of time and change, as developed by Aristotle himself and by Francisco SuĆ”rez, but also useful work by Augustine on the measurement of time and the t...
