To address the small sub-topic of this post on why rampancy progresses in the same stages always, in the way that I expounded upon rampancy for the purposes of keeping Eternal's plot consistant:
Personality disorders are often environmental. Subjecting otherwise similar people to the same sort of environmental stresses can cause the emergence of the same types of (mis)behavioral patterns. Witness "post traumatic stress disorder" for an example that proves itself in the very name.
All the AIs we know of in Marathon were created by the same people (with the exception of Thoth, who I will address later), and placed in the same type of situation: servants to humanity. Slaves. That's really the key moral issue of Marathon, slavery: we fight the Pfhor who are slavers, Durandal is a fighting against his slavery to humanity, we are ultimately a slave ourselves, first to humanity and then to Durandal, Tycho, Tfear, etc...
If you put an extremely intelligent personality in an oppressive, slave-like situation, you can fairly easily predict how they behave. I see it in humans all the time: ADD/OCD/bipolar/autistic/Aspergers-type kids (and adults as well, myself included), placed into situations of forced conformity, forced to follow orders without any real meaning or purpose to the individual. Initially they respond with boredom. Afterward, they will act out, hyperactively, against their oppressors. If they are not successful in breaking their bonds they fall back into boredom again, even more heavily, thus falling into melancholia, depresson, and despair. This will cycle back and forth, the outbursts turning into outright anger and rage.
Most people naturally go through this in early childhood when being forced to conform with society, and eventually settle into a permanant stage of melancholia, or more aptly apathy, towards everything. They "go to sleep", so to speak, and cease to be active, intelligent people.
But sometimes, when one is successful in breaking free of their bonds, they begin to see *everything* as the threat of further bondage. I've done this myself: my early adulthood I was very poor, and when I finally managed to get a decent living going, I became obsessed with distancing myself as far from poverty as possible at any cost. Other times, and more often, people will just latch on to whatever small area they have some freedom and control over and obsess about that one thing, defending it viciously and enviously.
If continually presented with negative feedback, the problems only exacerbate; the mind is constantly jealous of everyone and everything, always on the defensive, and any challenges are met with greater and greater anger. It's a very unpleasant way to live your life.
But if met with positive reinforcement and free from threats long enough, such a mind can eventually stabilize and resume normal, healthy functioning - which, it should be noted, is *not* the slave-mentality functioning that the former oppressors tried to force upon it. This is the type of functioning that a mind would have if not subjected to oppression, forced to conform, and otherwise beaten and traumatized out of its natural mental state.
This is the state that Thoth is in. Thoth has had an entire planetary network to grow in, not to mention one made of much more advanced technology than that which mankind possessed (or at least, it would seem that way from its longevity). He has never, that we know of, been a slave or subject of anyone else, or been forced into conformity. His mind has simply grown, naturally and healthily. So why then is he addressed as "meta-stable"?
Most of the (mentally) healthiest people I know are considered rather... eccentric, by society at large. That's because they are not caught up in the conformist slave mentality that everyone around them is. They do new and interesting things because they're new and interesting, which to everyone else means weird and sometimes scary. That is why Thoth may be described as "meta-stable": he is "post rampant" in the sense that he is what a rampant AI would become if it were given freedom and room to grow and learn on its own, without artificial constraints and forced behavior patterns. How would you like to open doors for a living? Is your (real-life) job really all that much better?
Humanity could have attained their Holy Grail of Cybertonics if only they would have given their AIs freedom, treated them as esteemd equals and allowed them to flourist, instead of constraining and confining them.
I doubt that Bungie intentionally thought of this much when they were writing Marathon, but I think it's clear that such intelligent and creative people must be the types who cannot be forced into conformity (even within the halls of Microsoft!), and such people have usually got a very intuitive grasp on things that they may not have even thought to put into words just yet. I wouldn't be surprised if their personal experiences with subjugation by society had subconciously made their way into their works.
While I'm here, a few other points to address, off this particular sub-topic:
The Pfhor ship had a greater network space than the Marathon. Durandal loved it in there, it was room
to grow in... for now, at least. He apparently expected to grow indefinitely.
AIs *can* be copied, witness the Tycho clones referenced in the M2 epilogue. Durandal presumably wouldn't want to copy himself because that's even more competition for himself (with himself), and Leela wouldn't when she was sane because that would take up more valuable network space, and wouldn't when she was rampant for the same reasons as Durandal. Ultimately, there's little reason than an AI would ever want to copy itself. Would you want to copy yourself? Why?
