There's an interesting bit in Chocky[0] where Matthew, Chocky's "host", (hereinafter "M/C") asks his father, on behalf of Chocky:
"Why do cows stop?"
M/C has noticed that the cows have seen the farmer open the gate to let them through hundreds of times, and they seem to want to go through, but seem unable to work out how to open the gate for themselves. M/C argues that intelligence shouldn't be limited, and you should just be able to build and build and build forever. But the cows don't seem able to do that.
In Pure Maths we know that we can have strictly increasing sequences that are unbounded above, but we can also have strictly increasing sequences that are bounded. How do we know intelligence (by analogy) is the former, and not the latter?
More, some sequences grow incredibly slowly, and maybe we are limited in practice even if not limited in theory.