Does Time Really Pass? Simon Prosser University of St Andrews

1. Does Time Really Pass? Simon Prosser University of St Andrews University of Durham Institute of Advanced Study Public lecture, 20th November 2012

2. Does Time Really Pass? Simon Prosser University of St Andrews University of Durham Institute of Advanced Study Public lecture, 20th November 2012 T

3. Does Time Really Pass? Simon Prosser University of St Andrews University of Durham Institute of Advanced Study Public lecture, 20th November 2012

4. Does Time Really Pass? Simon Prosser University of St Andrews University of Durham Institute of Advanced Study Public lecture, 20th November 2012

5. John McTaggart’s (1908) A-series and B-series t5 Distant future t4 Near future t3 is earlier than t4 andt5 but later than t1 andt2, etc. This is true at all times t3 Present t2 Near past t1 Distant past A-series B-series

6. The A-theory of Time Distant future The A-theory of Time: Time is best represented by the A-series Time passes. There is a metaphysical asymmetry between the present and other times. The ‘Common sense’ view. Near future Present Near past Distant past A-series

7. The B-theory of Time t5 The B-theory of Time: Time is best represented by the B-series Times are ordered, but there is no metaphysical asymmetry between the present and any other time; there is no objective ‘now’. Time does not pass. t4 t3 is earlier than t4 andt5 but later than t1 andt2, etc. This is true at all times t3 t2 t1 B-series

8. The Ontology of the A and B Theories = existing events = non-existing past or future events = the objective present ‘Moving spotlight’ A-theory ‘Growing Block’ A-theory Presentism (A-theory) B-theory

9. Four arguments against the passage of time • McTaggart’s paradox • The rate at which time passes • Einstein’s Theory of Relativity • The impossibility of experiencing the passage of time

10. Four arguments against the passage of time • McTaggart’s paradox • The rate at which time passes • Einstein’s Theory of Relativity • The impossibility of experiencing the passage of time

11. 1. McTaggart’s paradox • McTaggart (1908, 1921) held that the A-series leads to contradiction because if time passes then every event is past AND present AND future • He held that attempts to remove the contradiction by saying, for example, that the event was future, is now present, and will be past, fail because a new contradiction appears at the second-order level (e.g. the event must be future-future, present-present and past-past). • In recent years, however, this argument has increasingly been found wanting

12. Four arguments against the passage of time • McTaggart’s paradox • The rate at which time passes • Einstein’s Theory of Relativity • The impossibility of experiencing the passage of time

13. 2. The rate at which time passes • If time passes, how quickly does it pass? • Standard answer: one second per second! • But can we make sense of a rate of one second per second?

14. Four arguments against the passage of time • McTaggart’s paradox • The rate at which time passes • Einstein’s Theory of Relativity • The impossibility of experiencing the passage of time

15. 3. Einstein’s Theory of Relativity • If there is an objective present time then there should be a single, objective fact about whether the two rings are simultaneous • But according to relativity theory, if the rings are simultaneous for an observer at rest with respect to the bells then the rings will not be simultaneous for a observer moving as shown • Is there some privileged frame of reference that determines which events are present?

16. Four arguments against the passage of time • McTaggart’s paradox • The rate at which time passes • Einstein’s Theory of Relativity • The impossibility of experiencing the passage of time

17. Could we build a device that detects the passage of time? A B ✗ ? PASSAGE DETECTORTM

18. Why no physical device can detect the passage of time t5 Distant future t4 Near future t3 is earlier than t4 andt5 but later than t1 andt2, etc. This is true at all times t3 Present t2 Near past • Physics predicts the same series of events regardless of whether the A-theory or the B-theory is true. • So the detector would behave in the same way regardless of which theory was true. t1 Distant past A-series B-series

19. Why do we believe that time passes? … we are immediately and poignantly involved in the jerk and whoosh of process, the felt flow of one moment into the next (D. C. Williams, 1951)

20. Eddington on experiencing temporal passage … consciousness, looking out through a private door, can learn by direct insight an underlying character of the world which physical measurements do not betray. (Sir Arthur Eddington, The Nature of the Physical World (1928: 91)

21. The impossibility of experiencing the passage of time • So, the nature of experience gives us no reason to believe that time passes • However this might seem compatible with the claim that if time passes we can experience it passing • I shall now argue that even if time did pass, we could not experience it passing • Then, finally, I shall argue that it follows that time does not pass

22. Experiences map uniquely to worldly features E1 E2 Experiences E3 E4 E5 PT

23. Time does not pass • Suppose there were H-theorists, who believed that headaches were perceptions of H-properties instantiated by nearby clouds. They knew nothing else about H-properties. • Can an H-theorist accept that headaches have nothing to do with H-properties, but still claim that clouds have H-properties? • No: they have no understanding of which properties H-properties are supposed to be. • The obvious conclusion should be that there is no such thing as an H-property.

24. Summary • Our first three arguments - from McTaggart’s paradox, the rate of time’s passage, and Einstein’s theory of relativity – threaten the claim that time passes, but perhaps they are not conclusive • However our experiences give us no reason to believe that time passes • Even if time did pass, none of our experiences could really be experiences of time passing • Consequently we don’t even know what it would be for time to pass • The only reasonable conclusion to draw is that there is no such phenomenon as the passage of time, and the B-theory is correct.