There's something in linguistics called Folk Etymology. And basically what it is, is the sort of general/popular conception of a word, without the actual historical roots. Such formations include "outrage" being from "out + rage" instead of the Latin "ultra-".
And within this realm of folk etymology, there's a general conception of the regularity of prefixes and suffixes. That "-ness" can be applied to any adjective to denote the essence or ideal quality of that adjective. (deaf => deafness; bright => brightness; etc). Unfortunately, it's "stupidity", not "stupidness". (ref: random eavesdropped conversation on the GO train a while ago.)
And "-ity" has its own set of nouns: stupidity, inebriety, sobriety, sexuality, brutality, etc. However, like all things, even this has its exception. Consider: "university". Now, I have yet to see this word used in the context of describing the essense of the universe -- which would normally be universality. And, interestingly enough, this rule is preserved in German as well: stupidität, sexualität, universität, etc. Unfortunately, I'm too lazy to investigate the consistency of this phenomena in all PIE languages, but I have a feeling that at least in French, it's somewhat true as well ("-aire").
Another one that folk etymology would have us believe is "re-" being a prefix that exclusively means "again", like in repeat, rerun, redraw, readdress, reread, etc. And yet, there's also a set of words that have an oppositional nuance: reject, renounce, recant, repel, etc.
I find it both fascinating and somewhat frustrating to know that English (as well as most other languages) can't be consistent in even these small grammatical devices. But it adds to the languages; gives it character. Or in the case of "university", history.