The Complexity of Temporal Mechanics, Robot Friction and the audacity of cinematic sagas which think they need a fourth film

The Terminator franchise is probably one of the most well known, not only in this time but the future. For those pedants unaware of the concept;

The Terminator
In the distant future, humanity has created a sentient computer, Skynet, to which we entrusted our entire defence network to, so it could efficiently protect us from outside threats. It, in it's huge and humming mother board filled glory, decides that the only major threat to mankind is mankind itself. So, to protect us, it devises a plan in which it starts a nuclear war so we give it even more power. It then enslaves the species and keeps a few of us alive, for reasons unknown.
In the even more distant future (roughly now) rebels are causing quite the difficulty for the Masters of Humanity. So to try and stop us lot from being a pain, our tin-based masters have thought of this plan where they send back the Governor of California to stop Sarah Conner from ever spawning the leader of the rebels, John Conner. John is obviously a little worried at this point, and decides to send back Kyle Reese (who turns out to be his father, in a rather confusing twist of quantum-plot) so that Kyle can team up with John's mother to protect her. And so they can stop any of this from happening in the first place. Kyle, at this point, is unaware of the fact that he is the father of his commander, but probably realises that there's something going on post-love making.
They stop Arnie, protect her long enough for gestation to begin. But Kyle, the wonder-dad he is, goes and gets himself killed.

The Terminator 2: Judgement Day
Ten years later, our bucket based buddies send back another “Terminator” to kill the now (oddly pubescent for a ten year old) John, who is living in care, As his mother is in a mental institution for blithering on about walking toasters and Robot Rabbits which do a lot more than please lonely older women.
Future John catches wind of this and sends back a reprogrammed Arnie-bot 3000 (although where he gets it from is a mystery) to go and save himself from the Terminator Mark II. There's some side-plot where bits of the first Arnie have been found and are being researched by the eventual creators of Skynet.
This new bot has quite a few tricks up his ever morphing sleeve, and makes life annoyingly difficult for John, Sarah and Arnie. But don't worry, there's some really hot liquid metal to get rid of; him, Arnie, any of the files and research on the intelligent robots etc.
Now; as there is nothing to work on; surely there can't be a big-bad-bot, right?

The Terminator 3: Rise of the Machines.
Wrong.


I'll admit; my grasp on Quantum, the temporal or, even, science is somewhat lacking in existence. But there's quite a large issue I can't quite fathom with this time-travel lark. As an example;
John sends back Kyle to protect his mother. So she can then work towards stopping things from going down the shit-pan. But if none of this ever happened, then there would be no need to send back Kyle to inadvertently impregnate Sarah. And then there would be no John to send back Kyle, who helps stop the Arniegeddon. So it would happen anyway, so then John would send back Kyle to protect his mother. So she can then work towards stopping things from going down the shit-pan. But if none of this ever happened, then there would be no need to send back Kyle to inadvertently impregnate Sarah. And then there would be no John to send back Kyle, who helps stop the Arniegeddon. So it would happen anyway, so then John would send back... You see?
Now I know this is picked up on in Rise of the Machine. John and some wench are in a cave, like the terrorists they are, and John realises that his whole life has been pre-determined [Side Note 1]. He then knows that everything he will do will be pointlessly repetitive and will amount to very little, the robots will always rule and everything they attempt to do in the past will do nothing as it is in the past (however, there's quite a nice message in all this. That you shouldn't be too focused on the past, but more on the present and future. But I'm sure that is a little tough to decipher through all the epic explosions and catchphrases). All very depressing if you ask me.
Also, how clever can these robots be if they've never thought about temporal predestination? [Side Note 2].

If we're going to start getting really pedantic about the entire concept..
John mentions that the only reason Arnie and himself had no weapons, Arnie looks like a bloke and they're both starkers; is that “Only organic matter can go through time”.
When you say organic, how exact is this? Because there's iron, potassium (which make up, a fairly vital part of our bodies, THE BONES), magnesium and some other none-biological matter which feature inside us. Exact enough for Magneto to kill a bloke in X-men 1 [Side note 3]. Surely Kyle would feel a little bit “woozy” after going through the machine? He'd be missing some, albeit, fairly none-consequential vitamins (enough for his body to feel significantly different to how it does when working with all its parts). He'd need a good long kip and some decent food to counter-act all this time-travelling business.
And how is it that 3 inches of skin manage to confuse the Tardis from not realising that Arnie's a Furby? I'm not sure we should be trusting this machine, If it can't tell that under all that bravado beats the cold robot heart of evil-programming.
If nothing but organic matter can go through the temporal bubble, how can in, Judgement Day, Stretch Armstrong get through? He changes quite frequently into not only other people, but quite pointy objects. Christ Alive, that lass in the third one grows a gun from her elbow! They don't bleed like Arnie. His is actually organically covered, at least. They're some strange metal.
Like Arnie's gun-ridden body, there's too many holes in the idea to completely finish. I can't even begin to get started, without the fear of some deadly seizure taking hold and caressing me into the sweet embrace of death. But maybe someone will send back a machine to save me, but we all know how that ends.

I'm going to confess something now; I haven't seen the fourth Terminator film.
This isn't because I haven't managed to “get round to it” like so many episodes of “The Sopranos”, but because in my mind it doesn't exist. It's a little like the fourth Indiana Jones film.
Sorry?
Oh yeah, that doesn't exist either. There's only 3 of each.
But from what I do know about it, other than Christian Bale being an awful piece of biology, is that it does seem to ruin the whole idea which the only 3 REAL films set up.
Leave it at three, it's the magic number. And don't even try to justify “The Sarah Conner Chronicles”.


Side Note 1: http://en.wikipedia.org/wiki/Predeterminism
Side note 2: J. Kenneth Grider
Side Note 3: Just see X-Men 1. It's a pretty good film anyway.