Well on classification, an example of a classification is something like say, AIDS, which is a classification of the observational symptoms, while HIV is the cause. HIV if left untreated, will inevitably lead to AIDS.
But if we don't know what causes AIDS, then all we can do is make blind correlations, and we can't really do anything about it other than be mystified by this mysterious ailment. And there are many many things that could be correlated with AIDS patients, even if those correlations may not have anything to do with each other. Only by knowing the causation that HIV will lead to AIDS, that we can do something about it.
A lot of the stuff, if not everything in Socionics is about making correlations between classifications.
Some people may confuse the 8 functions and Model A as the cause, but it's not, they're classifications. It's like saying AIDS is the cause of AIDS. It's like analyzing the lack of immune system in a patient and saying "This is AIDS! AIDS is real!". Well... yes! But why? What causes it?
Anyway, I'm sure by keep asking the question "Why?", we will lead to more general theories about why should something be this and not that. In order to know that HIV causes AIDS, we'll need an entire theory of biology to explain it. No such theory that can explain cognitive causality exist in psychology yet. It's difficult to explain why should X -> entrepreneur. That's why so many people remain mystified and not enlightened.
What I mean by "limitless" is that, just as you can program virtually any kind of program into a computer, the human mind is capable of virtually any kind of cognition, whether it's flights of fancy, or a scientific theory that can accurately describe reality to a certain extent. There is no limit to what the combination of logic can produce, as that is infinite.
There are limits to how much information that can be processed, but that can be outsourced or offloaded to something else, like pen and paper or a computer.