Agreed, but that's a different issue. My question is, in the examples of the first three movies and the instances of Skynet/Resistance time travel, doesn't John have to launch a preemptive mission to the past in order to have any hope of affecting the outcome? T1 would otherwise have been successful in his mission eventually if not for Kyle Reese. The T-900 likewise if not for T2 and the T-X if not for T3! In each instance there is an attempt to protect Skeynet's target in the past with a time traveler ordered to protect Sarah Connor and/or John Connor. If Skynet is first to send any Terminator, the T-800, T-900 or T-X then it should meet no resistance from the future and eliminate John Connor's influence on subsequent events.
X
You are making the mistake of assuming that the time travel even happens in the future, and then changes made to the past propagate into the future. This requires multiple time dimensions and is incorrect. In essence, you have the order of things backwards.
The past effects of the backwards time travel happen before the backwards time travel occurs. It doesn't matter when Kyle steps into the time macchine, or in what order. All that matters is when he appears in the past, and where, and what actions he takes there.
From John Connor's perspective, and the perspective of an outside observer, the events of The Terminator and of Terminator 2 have already happened. They're written in stone before Skynet even builds the machine.
If events cannot be changed in the past, if everything must remain self consistent and any changes made to the past cannot change the future, then why would Skynet send the T-800 back to make changes anyhow? We also know that this is not the case, at least for the earlier time line where John is not related to Kyle. Also not true since something changes after the CTC is created ( or maybe it isn't yet) since T3's record of the future is different from that of T1 & T2.
As I stated, Terminator 3 isn't consistent with how real time travel works, and thus can be ignored for the purposes of examining time travel in the original film. Assuming that time travel in The Terminator resembles real time travel in any way, then there is not and cannot ever have been a timeline in which John Connor is not Kyle Reese's son.
There is only one time. While time is relative for different observers depending on things like velocity and position in space-time, there is always only one order of events. While time travel results in effects that precede their cause, it does not and cannot result in new timelines.
From the point of view of an observer on Earth, outside of the time loop, the Terminator and Kyle Reese appear first in 1984 for no apparent reason, and then disappear in 2029 when they use the time machine. This is, in a sense, absolute time. This is the order of events from the perspective of the universe at large, and is immutable according to the self-consistency principle.
The order of events is determined by absolute time, not by subjective worldlines. From the perspective of the Terminator and Kyle, the arrive in 1984 only after leaving 2029, but it is important to separate the subjective worldlines of individuals within a CTC from objective absolute time. While from their perspective, 1984 occurs after 2029, from all outside perspectives, 1984 comes first. Because 1984 comes first, the effects of their time travel are already set in stone before the time travel occurs.
Time
Travel Cannot Create or Destroy Matter/Energy and Connot reverse Entropy. This is very important. A time machine would easily become a perpetual motion machine if this were not the case.
This is, in fact, another argument for self-consistency, and another way to explain it. If time travel can alter the past, then it can be used to create an infinite amount of energy by generating conditions such that an object is sent to the present from the future, and then not sending that object when the time to do so arrives.
There is only one itteration of a time loop, not many.
This, again, connects mainly to the issue of conservation of Matter/Energy and the fact that there is only one absolute time. From the perspective of the universe, the time loop occurs only once. A time loop that itterated indefinitely would produce an infinite amount of energy as an infinite copies of the same time traveler would result. An infinitely itterating loop that did not produce multiple copies of a thing would fail due to entropy. Both are inconsistent.
For these reason, we must take the loop as seen by an outside observer at face value, that it occurs only once, and does not itterate.
The Many Worlds Interpretation Does Not Apply to Macroscopic Time Travel Effects
The Many Worlds Interpretation is very specific in its meaning and application. It only applies to probabilistic quantum wavefunctions, such as radioactive decay and the trajectory of a photon. It does not apply to macroscopic events, except in when macroscopic events are incluenced by probabilistic quantum events, which is rarely.
In the case of time travel, the probabilistic wavefunction is the "light cone" of the time traveler, the exact position and trajectory at which he enters the past. The Many World Interpretation that for every position and trajectory in the light-cone there is a universe in which the time traveler came into the past at that point with that trajectory. However, each of these worlds is entirely self-consistent, with the time-travel effects both pre-written and unalterable.
The self-consistency principle further limits the potential light cone of a time traveler because it cannot create inconsistent macroscopic effects, which means that Reese must be in a position to rescue and impregnate Sarah Connor in every world, the light-cone simply does not extend to positions where he cannot do so.
These facts together can only bring us to the conclusion that the backwards time travel presented in The Terminator, is a self-consistent closed loop, as any real backwards time travel must be.
It also leads us to the conclusion that there is not, ever was, and could never have been, timeline in which Kyle Reese did not backtravel.
Skynet's motives for time travel are a mystery that only Skynet can answer, but the reality of backwards time travel cannot be denied. If backtravel is possible, then it must be self-consistent.
T2 attempts to shed a ray of rope without being too specific, while T3, TS, and T:SCC are all totally incompatible with real time travel physics.
