I think it stands better to reason that once intelligence evolved, selective pressures for greater intelligence rapidly faded.
That's just a different way of expressing the same thing I said.
A brain that's too complex or powerful might "overshoot" the needs of existence within the universe and thus be just as unable to function as a person weighed down by dozens of extra limbs would be. The inner complexity of its thoughts might overwhelm its perception of the much less complex exterior universe and leave it incurably schizophrenic, say.
There's a mechanism that prevents our own imaginations and memories from doing so.
No, there isn't. That's why schizophrenia exists in the first place. We all have an inner mental life alongside our external perceptions. At healthy levels, we call it imagination. People who are more intensely imaginative tend to be writers, artists, scientists, inventors, priests, mystics, etc. But take it too far and the inner reality overwhelms the outer. Your fantasies become more real to you than the outside world. That's schizophrenia.
The only preventive mechanism here is balance -- having a degree of imagination, of internal mental activity, that's not out of balance with the needs of perceiving and interacting with the external world. Take any aspect of consciousness too far and it becomes insanity.
These are nice and generally correct sentiments--I'm not sure that "balance" is a cognizable factor, and individuals certainly do not attempt to balance anything, and "unbalanced" adaptations are well represented in nature.
Balance means avoiding runaway extremes, finding a viable middle ground between too little of something and too much of it. In evolution, those things are functions of the needs of your environment. I'm not talking about some Platonic ideal here, but about functionality, about having traits and abilities that are in balance with the demands of your environment, lifestyle, and biology. Having more than two eyes would place excessive, unnecessary demands on our brains and metabolisms, because we'd need that much more neural complexity to operate them and that much more food to power that extra organ and the extra neural processing to go with it. The cost of having extra eyes outweighs the potential benefits; it would be imbalanced. Conversely, having only one eye would save on metabolic demands, but it would deprive us of depth perception and field of view. Again, the cost would outweigh the benefits, which is imbalanced. For us, given the specifics of our environment, our behavior, and our anatomy, having two eyes is more balanced than the alternatives: the cost is commensurate with the benefit.
To clarify, are we talking about a naturally evolving life form, or an artificial intelligence? Huge difference--and I'll concede that evolutionary factors place major constraints on the natural development of an intelligence.
Any intelligence would have to be able to function within the environment it occupies. Sure, theoretically you could artificially create a brain that's vastly more complex than it would need to be to function in this universe, just as theoretically you could engineer a human with six eyes. My point is that it might not
work as well because it would be overkill, out of balance with its needs. Maybe you could make a superintelligent mind, but its internal processing might be so much more complex than the inputs it's receiving from the outside world that it doesn't even notice physical reality. By our standards, it might be schizophrenic or catatonic.
Not to mention that intelligence is a complex, dynamic process. There are a lot of ways it can go wrong. The more complex the system becomes, the greater its potential for instability. So there might be a threshold of complexity beyond which runaway chaos becomes inevitable.
The point is, we just don't know enough to make assumptions. We have a very, very small sample of sapient species to examine, and no examples of sophonts more intelligent than the greatest human minds. We have no grounds for assuming that intelligence has no functional upper bound. We like to think of our intelligence as something extraordinary, something intangible that makes us special, even something divine. It follows from that to think of it as something that can be escalated without limit. But the more we learn about intelligence, the more we discover that we're not so different from other animals; we don't have much of anything they don't have, we just have more of it in one package. Intelligence is a biologically evolved trait that arose in response to survival needs. And most biological traits have their limitations on how far you can augment them before they become maladaptive. So I think it's overly romanticizing intelligence to assume it must be fundamentally different from every other trait, to assume it has no upper bound.
