TED SIDER A and B Series

What is the role of personal time?

Other views on nature

of external time

• External time is not similar with personal time

• Time has an intrinsic direction, which is irreducible to causation, entropy or anything else

• External future: concerns stages that are forward in the intrinsic ordering of time

• Time traveler’s personal future: concerns stages that are causally and entropically downstream from current stage

• Lewis stated that personal time ‘’isn’t really time, but it plays the role in (the life of a time traveler) that time plays in the life of a common person’’ (1976, p.70)

• In order to determine whether Lewis is right,

• The nature of the external time need to be explained in more detail within the concepts of past and future.

Presentism -> only currently existing entities exist

Eternalist View

• Reductionism about tense: tensed statements have tenseless truth conditions

• Reductionism about the direction of time: the direction of causation or perhaps to some asymmetry in matters of particular fact such as entropy

• According to eternalism, personal time and external time is similar

Eternalism

• Does that preclude time travel?

• A present-tense statement embedded in a past-tense operator such as; ‘’It was the case that two hundred million years ago that Katy exists’’

• Keller and Nelson on translating David Lewis’ account into presentist terms

Personal Time and External Time

• Spatializing account of time

• Past=Present=Future

• Socrates, me and Sofia’s husband in the future are equally real

• According to Lewis, time travel involves a ‘’discrepancy between time and time’’

• A paradoxical utterance -> ‘’in two minutes I will gaze upon a dinosaur’’

• I would not be a time traveler, only a person that once viewed a dinosaur, two hundred million years ago.

• Lewis’ solution -> ‘’personal time’’ and ‘’external time’’

• Increasing entropy within the future direction of personal time

• A reversed causation sync within the time traveler

Time as “Growing Block Universe”

Growing Block Theory is the thesis that temporal passage is a fundamental feature of reality. The future end of the growing block universe is defined as the end onto which “new layers of being” are being added. Broad’s most fundamental form of change: becoming. Becoming is coming into existence of events.

C.D. Broad's Argument

• Nothing has happened to the present by becoming past except that fresh slices of existence have been added to the total history of the world. The past is thus as real as the present.

• The essence of a present event is, not that it precedes future events, but that there is quite literally nothing to which it has the relation of precedence.

• The sum total of existence is always increasing, and it is this which gives the time-series a sense as well as an order. A moment t2 is later than a moment t1 if the sum total of existence at t2 includes the sum total of existence t1 together with something more.

TED SIDER A and B Time

Time as “Growing Block Universe” on reductionism about direction

Time as “Growing Block Universe”

on reductionism about tense

• “There once were dinosaurs” could be regarded as true iff there exist dinosaurs located before the utterance. But no true claim about the future could be reduced in this way if the future does not exist.

• “People will still live on Earth in two hundred years” is true iff there exist humans living on Earth that are located two hundred years after that utterance. The utterance turns out false if future objects do not exist.

• External future is extremely different from personal future. External future is not of a sequence of genuinely existing stages, since future does not exist; whereas personal future of someone who travels into the past is a sequence of genuinely existing stages.

• Directionality of personal time reduces to causation or entropy, whereas this is not true for the direction of Broad’s external time.

C.D. Broad rejects components of spatializing account of time by claiming

• Past and present objects exist but future objects do not. Broad can be considered as half presentist or half eternalist since he claims only past and present exist. (eternalism)

• Past-tensed statements may be given tenseless truth conditions, future-tensed statements cannot be. (reductionism about tense)

• The direction of time for Broad is not reducible to entropy or causation. (reductionism about direction of time)

Phil 487 - Metaphysics Through Star Trek

Back to Presentism

Presentist rejects each component of the spatializing picture:

1. Neither past nor future objects exists

2. Tensed statements are irreducible

3. The direction of time is not a matter of causation or entropy; it is a matter of the difference between the sui generis past-tense operators and the sui generis future-tense operators

• The presentist can appeal instead to sequences of tensed statements describing causal and qualitative facts.

Thus,

• my personal future concerns a network of past-tense causal statements about me.

• quite different than the nature of my external future, which doesn't concern causation at all, and which concerns future-tensed statements.

• “There exists a dinosaur-viewing by me, located two hundred million years before the present time.”

• Presentist version: “It was the case two hundred million years ago that I am viewing a dinosaur.”

Two-place causal relation vs two-place tense operator

• my entry into the time machine and my viewing a dinosaur
• “because Φ, it was the case n units of time ago that Ψ”

Third fact about presentism

• What renders external time dissimilar from presentist personal time

• External future consists of facts expressible with future tense operators as it will be the case that

• For personal future, everything Lewis says about personal time can be translated into tensed terms

• Personal time does not “play the role that time plays in the life of a common person.”

• “In two minutes I will gaze upon a dinosaur.”

• A presentist can say “gazing at the dinosaur is in the future in my personal time.”

• ”personal time” is merely an invented quantity, and is misleadingly named at that.

• Anticipation of seeing a dinosaur or fear of being annihilated by a device misleadingly called a “time machine”?

• What does this device do?

Conception of Tense Operators

• Most of the presentist are anti-reductionist.

Primitive "Undirected" Binary Tense Operators

Therefore, if presentists change their preference on the concept of tense use, there would be no conflict between presentism and time-travel.

• Presentists can use the primitive phrasing:

"it IS the case five minutes “away from” now that φ and it IS the case five more minutes away from now that ψ."

• Past and future have their distinct tense operators according to them and that causes the divergence between personal time and external time.

• It gets personal time closer to external time and states the fundamental facts by avoiding the obstacle of tense use.

• Presentists, by using this primitive way of syntax, can get closer to the idea of Lewisian time travel.

• Is there an alternative way of stating the fundamental facts for a presentist?

Thank your for listening

Nur Fenercioğlu

Dilara Sökmen

Emre Bilgin

Can Bozkır

Alper Sarı