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Time Travel/Lewis: thesis: it is possible. - The paradoxes are merely curiosities. - They involve a discrepancy between time and time - problem: how can the same event (departure and arrival) be separated by two time distances with different length. - Wrong: to postulate several time dimensions. - For the time traveler would not be able to find his comrades on a surface.
Solution: separation of external time and personal time of the traveler, as measured by his clock - no matter what happens to the clock - we do not want to define time operationally, but functionally. - I.e. the clock is infallible by definition.
Functional role in the event pattern of time traveler. - E.g. his hair is growing, but that is not time, but only the same role as in normal life. - It is the personal time of the traveler - this is sufficient to transfer the temporal vocabulary.
Time travel: the life of the traveler is like a railway track: e.g. a place 2 miles east might as well be a place 9 miles west. - E.g. loop: the track crosses an earlier section of itself once - external time: unique encounter - personal time: repeated - Event: separated in the personal time, united in the external time. - Time Traveler: is not there twice in full person, but in two full states. - (> Person state) - Problem: What unites these states. - (Unlike normal people, no problem). - Different problem: if the time travel is instantaneous, there is a break in the time line. - Then there are two people and none of them is the Time Traveler.
Time travel/Causality: 1) the time travel requires personal identity and thus causal continuity. - Thus reverse direction. - The direction of counterfactual dependence and causation is controlled by the direction of other asymmetries of time, so reverse causality and thus causal loops cannot be excluded. - That does not mean that the loop as a whole is the cause or can be explained. - Problem: information transfer - e.g. if the information must be transmitted first to build the time machine, there is no solution. - The person and person states of the time travel have to be defined simultaneously. - Otherwise, they will be assumed to be mutually circular.
For the journey we only need three-dimensional space without time as a fourth dimension.
Time travel/Grandfather paradox: the past cannot be changed, because moments cannot be split into temporal parts which could be reversed - murder of Grandfather is either contained timelessly in the past or it is timelessly not contained. - Wrong: Original and new past: instead: one and the same localized twice (like railroad crossing in eight-shaped railway track). - So killing during Time travel is a contradiction: both killing and not killing - but past no particular character. - Also present and future unchangeable, because their moments have no temporal parts. - ((s) developments may probably be influenced.) - Can is ambiguous: a monkey cannot speak Finnish, because of its anatomy, I can’t speak it, but I have not learned it. - Narrower and broader set of facts - Murder of grandfather possible because of narrow set: everything you need for murder - but no more set: father-son relation, the end of life of the grandfather, etc. - Branched time: (branching after the murder of the grandfather) no solution, because the past is not changed. - It is consistent that the grandfather is alive and dead, but in different branches, but there are not two events._____________Explanation of symbols: Roman numerals indicate the source, arabic numerals indicate the page number. The corresponding books are indicated on the right hand side. ((s)…): Comment by the sender of the contribution.
Die Identität von Körper und Geist Frankfurt 1989
Konventionen Berlin 1975
Philosophical Papers Bd I New York Oxford 1983
Philosophical Papers Bd II New York Oxford 1986
Cl. I. Lewis
Mind and the World Order: Outline of a Theory of Knowledge (Dover Books on Western Philosophy) 1991