Skynet isn't omniscient, it only know's where Sarah Conner is at a specific time period, presumably the amount of information available in the future is limited (destroyed, ironically in the war).

It doesn't even know what she looks like, where she is. Only that she's called Sarah Conner and was in a specific area of LA during that time period.

Of course, if it succeeds, it becomes a paradox, but for Skynet, which has effectively lost the war, so that doesn't matter, its a 'hail mary' pass - Whatever the outcome, its better than being destroyed.

John Conner, has no choice, but to effectively stop that happening, and in doing so probably changes his own fate somewhat but not extensively (in fact arguably it probably results in a better equipped John Conner in the future).

It doesn't even ensure that humanity will lose the war either, only that it will change it, by changing the leader.

Skynet also, can't go too far back. It can't wipe out the human race, before it exists. Nor can it risk its own existence by changing the past either.

"One Nation Under God, has turned into One Nation Under the Influence of One Drug"
[Link]

So what you are saying is that because no destructive paradox occurred then it's OK.
The problem is that by sending a time traveler back, you would take an unacceptable risk of a butterfly effect that could change the entire future and erase your own existence.
Equally, anything that you alter in the past has effectively already happened from you point of view so is therefore a matter of record. That means you could check to see if something had changed. That would render it useless as a tactic. John Connor sending his own father back is also a causal loop which would mean that in theory, he had no free will in making that decision and that he came into existence from nowhere.
I have a big problem with that.

Edited by Hrolf The Ganger (27 Feb 2017 4.52pm)

This almost made me spit my beer out

I'm a blind man, i'm a blind man, now my room is cold,
When a blind man cries, Lord, he feels it from his soul.
[Link]

Also, technically, its a Husker Du sweatshirt... but...

"One Nation Under God, has turned into One Nation Under the Influence of One Drug"
[Link]

Yes, but that's from a perspective within time and space. The ability to travel into the past, and allowing for a non-deterministic universe, means that any change would be the 'already happened' and that must then re-inform the future, implementing a butterfly effect.

I think the idea of the 'creates an alternative universe' provides a decent explaination. For me, I see it that there is universe 1 in which John Conner isn't Reese's son, where he discovers that the terminator has been sent back in time to kill Sarah Conner - and universe 2 in which Reese becomes JC's father.

We follow the events only in Reese's memories of Universe 1 and in the action that occurs once the T-800 and Reese have come back in time (and thus created Universe 2).

But here we see the break down of the reliance of an point of observation, a singularity point in essence, where the observer is only capable of seeing actions within our perspective. Its also not necessarily true of all observers either, as the time traveller(s) will have memories of a future that 'no longer exists' - or possibly have constantly shifting memories as the events they change in their now present, potentially change their future.

As Reese existence is not long enough to establish what happens once you change time significantly to affect your own past.

I think the alternative universe theory of time travel makes sense, at least in terms of a thought experiment to get your head around the fact that both universe 1 and 2 can exist in a kind of f**ked up cat in a box kind of way.

"One Nation Under God, has turned into One Nation Under the Influence of One Drug"
[Link]

I think the multi timeline version is the only one that can exist in reality.
In the single time line theory any journey into the past would erase the version of that person in his own time. He would therefor no longer exist as his original self and only as himself in the past. Potentially he could therefore have done none of the things that he had done as his original self if he ever existed at all. He would therefore have no memory of any future since it never happened in the first place. More importantly he might not have traveled back in time in the first place rendering the whole loop a non starter.
The past is always the past no matter who you are or where you observe it from. The future is always the future.
What that means is that if you could see the future it would also be of no use at all because the future is a direct result of the past and therefore unchangeable.