TIME Introduction to Metaphysics Lecture 9

Two Intuitions Time flows and, as it passes, things change. Suppose that a God-like being, existing outside of time, observes the universe. She would see a static, unchanging block.

Some Questions Does time flow? In what sense do ‘things change’? What would the universe look like ‘from the outside’? Is time real?

Sharpening Our Intuitions McTaggart (1908) introduced two ways of (chronologically) ordering events. From the past, through the present and to the future. This is the A-series. From earlier events to later events. This is the B-series.

The A-Series Captures the intuition that time flows: an event which is now present, was future, and will be past. PRESENT FUTUREPAST World War 2 The moon landing You are born This lecture You graduate Queen Elizabeth coronation King Charles coronation First humans on Mars PRESENT FUTUREPAST

The B-Series Captures the intuition that, viewed from outside, the universe is static: if one event is ever earlier than another, it is always earlier. World War 2 The moon landing You are born This lecture You graduate Queen Elizabeth coronation King Charles coronation First humans on Mars earlier later

PART 1 MCTAGGART AND THE UNREALITY OF TIME

McTaggart’s Argument McTaggart (1908) argues that time is not real: (P1) If time is real, then events form an A-series. (P2) No events can form an A-series. (C) Time is not real.

McTaggart’s Argument (P1) (P1) If time is real, then events form an A-series. McTaggart claims: if time is real, then there is genuine change. He then argues that there can only be genuine change if events form an A-series.

McTaggart’s Argument (P1) Why can there only be genuine change if events form an A-series? Consider an event: the moon landing. The event is a moon-landing, it has certain causes & effects, it involves Neil Armstrong... The event always has these characteristics. The event only changes in one respect: it was future, then present, and is now past. So it changes only if it is in an A-series.

McTaggart’s Argument (P2) (P2) No events can form an A-series. First: past, present and future are incompatible determinations. An event cannot be both past and future, both present and past, etc. McTaggart argues that, if events form an A- series, then each event is past, present and future. This is a contradiction.

McTaggart’s Argument (P2) PRESENT FUTUREPAST The moon landing You are born This lecture You graduate PRESENT F.PAST The moon landing You are born This lecture You graduate Recall that the A-series looked like this: So, this lecture is in the future. But the A-series also looked like this: So, this lecture is in the past.

McTaggart’s Argument (P2) PRESENT FUTUREPAST The moon landing You are born This lecture You graduate PRESENT F.PAST The moon landing You are born This lecture You graduate Recall that the A-series looked like this: So, this lecture is in the future. But the A-series also looked like this: So, this lecture is in the past. CONTRADICTION

McTaggart’s Argument (P2) PRESENT FUTUREPAST The moon landing You are born This lecture You graduate PRESENT F.PAST The moon landing You are born This lecture You graduate Recall that the A-series looked like this: So, this lecture is in the future. But the A-series also looked like this: So, this lecture is in the past.

McTaggart Argument (P2) Can we avoid the contradiction? Perhaps we should say: this lecture was future, is present, and will be past. But, then, different stages of the A-series take place at different times. If real change occurs, these stages had better form another A-series.

McTaggart’s Argument (P2) Such an A-series would look like this: PRESENT FUTUREPAST PRESENT FUTUREPAST PRESENT Moon landing You are born This lecture You graduate PRESENT Moon landing You are born This lecture You graduate PRESENT Moon landing You are born This lecture You graduate PRESENT Moon landing You are born This lecture You graduate

McTaggart’s Argument (P2) McTaggart’s contradiction now re-arises. Consider the stage of the A-series at which this lecture is present: This stage is, by the same reasoning as before, past, present and future. To avoid the contradiction, we need another A- series. Thus, McTaggart concludes, avoiding the contradiction leads to a vicious infinite regress.

McTaggart’s Argument (Summary) (P1) If time is real, then events form an A-series. – As time requires change, and there is only change in an A-series. (P2) No events can form an A-series. – As the A-series leads to contradiction or infinite regress. (C) Time is not real.

PART 2 THE A-THEORY OF TIME AND PRESENTISM

The A-Theory of Time The A-theory of time: Time is real, and it flows. To make sense of this, we want an account of what the universe is like. One suitable account is presentism.

Presentism Presentism (defended by e.g. A. Prior): Only the present is real. The past and the future do not exist. The present, and other things that exist, change.

Presentism and the A-Series For the presentist, we should not take the A- series literally. There are no past or future events for the present to move between. For the presentist, then, no event can be past or future. This avoids McTaggart’s contradiction.

Talking about Other Times How do presentists talk about other times? E.g.: “Humans landed on the moon” Does not mean: humans landed on the moon in the past. Instead means: it has been the case that humans are landing on the moon.

Problems for A-Theory + Presentism How quickly does the present change? (JJC Smart) – And: at what rate does time flow? – There should be an answers to these questions. But there aren’t… What about the theory of relativity? – No absolute simultaneity, so no real present.

PART 3 THE B-THEORY OF TIME AND ETERNALISM

The B-Theory of Time The B-theory of time: Time is real, but it doesn’t flow. To make sense of this, we want an account of what the universe is like. One suitable account is eternalism.

Eternalism Eternalism (defended by e.g. JJC Smart): There is nothing special about the present. Past, present and future all exist (in the same sense). Roughly, ‘the time dimension’ is just like another space dimension. (Spacetime.)

Eternalism and Change For the eternalist, the universe is a bit like a B- series. But (contrary to McTaggart’s argument) this need not imply that there is not change. Events do not change from being future, then present, to past. Objects change: they have different properties at different times.

Problems for B-Theory + Eternalism They fail to capture the apparent fact that the future is open. It is unclear how to explain the vividness with which we consciously experience the present (but not the past or future).

Brief Bibliography Loux, M. (ed.) Metaphysics: Contemporary Readings (2 nd Edition). New York and London: Routledge. McTaggart, J The unreality of time. Mind 17(68): 457–474. Prior, A The notion of the present. In Loux 2008: 379–383. Smart, JJC The river of time. Mind 58(232): 483–494.