Bardon - A Brief History of the Philosophy of Time

A BRIEF HISTORY OF THE PHILOSOPHY OF TIME

Adrian Bardon

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Library of Congress Cataloging-in-Publication
Data Bardon, Adrian.
A brief history of the philosophy of time/Adrian Bardon.
pages cm

ISBN 978-0-19-997645-4 (alk. paper)ISBN 978-0-19-930108-9 (pbk. : alk. paper)
ISBN 978-0-19-997773-4 (updf)ISBN 978-0-19-997774-1 (epub)
1. Time. I. Title.
BD638.B335 2013 115dc23
2012045782

1 3 5 7 9 8 6 4 2
Printed in the United States of America
on acid-free paper

For Janna, Zev, and Max

I am very grateful for the extensive comments given on drafts of this work by Heather Dyke, Craig Callender, L. Nathan Oaklander, Barry Dainton, Yuri Balashov, and Eric Schliesser; I am also grateful for the comments by six anonymous reviewers selected by Oxford University Press, and Greg Cook generously clarified a number of issues.

I used this book as a text in several recent editions of my Philosophy of Space and Time course; I am grateful for the responses I received from my students.

Marcia Underwood kindly rendered the illustrations in digital form; her creativity and design talents improved them in many ways.

My wife, Janna Levin, read the manuscript more than once, looking for errors and providing helpful comments.

A BRIEF HISTORY OF THE PHILOSOPHY OF TIME

What makes time so elusive? Time couldnt be a more familiar and fundamental part of our existenceand yet, as soon as we really start thinking about it, we find that there is no subject more mysterious and ineffable. Ineffable is a particularly good way to put it: It means beyond words. It is difficult to get started in thinking about time, because it is difficult even to put our thoughts about time into words.

The basic problem has been under intense consideration throughout recorded history. There are two essential facts about time that most will agree on. First, we think of events as arrayed in a sort of order, where what is happening depends on where we are in that order. Second, we think of events as coming to be and passing away, as undergoing change over, or in, time. (Roughly speaking, we use calendars to track this first aspect of time and clocks for the second.) But these two characteristics seem to be in tension: If events are arrayed in an order, then how can we also say that they come to be and pass away? Is the passage of time real, or is it merely a subjective aspect of our experience? What is it for an event to be in time in the first place? Upon reflection, it is very difficult to explain just what a temporal description of the world really amounts to.

This fundamental conundrum gives rise to a number of significant subsidiary questions. What is the nature of our experience of time? What gives time its direction? Is travel in time possible? Is the future unwritten, and do our choices matter? Did time begin, and, if so, how?

This book concerns the philosophy of time. One might well wonder how a philosophical approach to time is different from a scientific, psychological, sociological, literary, or other approach to the subject. Answering this question requires that we briefly examine what philosophy is.

To be honest, philosophers generally dread being asked to explain what philosophy is. Part of the problem is that philosophy is more of an activitythe activity of philosophical thinkingthan a subject matter, so it is easier to demonstrate than to define. Unlike physics, mathematics, literary studies, religious studies, or just about any other field of investigation, philosophy does not have its own, unique subject matter: A given philosophical investigation might, for example, concern itself with the subject matter of science, or math, or art, or religion. Philosophy is really distinguished by the kinds of questions it asks. Philosophers ask foundational questionsquestions about, say, science: What is a scientific explanation? What is causation? What is the proper domain for empirical study? Philosophers ask questions about art: What is beauty? What counts as a work of art?

There is an unwarranted prejudice that philosophers like to dither around and ponder unanswerable questions. Nothing could be further from the truth, at least as far as contemporary academic philosophy is concerned. Thinking about philosophical questions is not viewed by philosophers as some sort of meditation, with no real endpoint. Philosophers deal in tough, abstract questions, but they shun unanswerable ones like the plague. Indeed, distinguishing between questions that are hard to answer and questions that are meaningless or otherwise poorly formed is a big part of the philosophical enterprise. The inherent difficulty of philosophical questions can make progress very slow, and this may be confused with a lack of progress.

To get a better grasp of what time is all about, philosophers have two main jobs to do: figure out exactly what questions to ask, and then figure out how to answer them. The first of these jobs is often the tougher one, and is commonly the main task in serious philosophical work.

In understanding the question What is time? we start by trying to zero in on our target. Figuring out what you are asking when asking about time is less than straightforward. In ordinary discourse, we employ temporal terms, like past, present, and future, without thinking much about what they mean. In describing the world, natural scientists tend to presume an understanding of temporal concepts, like temporal measurement, succession in time, or the earlier/later relation, in their accounts. Before we can formulate questions about time, we need to look carefully at what our notions about time include, and what facts and concepts we take for granted in both colloquial and scientific discourse.

Time certainly has something to do with measurement. This doesnt tell us much so far, because what time measures is duration, and duration is a temporal concept. Time can also be thought of as a coordinate system. Events are located in time; they have a fixed temporal position relative to each other. This means something different from having a different spatial position, or a different position on a number linebut how, exactly? Finally, time has something to do with change. Again, this is just a starting point, because it is very tough to see how we could understand what