My Answer (see previous post)

Vowels seem to give an amount of continuity and certainty, connecting the "real" sounds with by certain designated open sounds. Besides giving us a greater range of possible words (thereby increasing our ability to communicate, create, and exert dominion over the earth), it seems vowels are indicative of the "do fully" rather than the "get by" mentality that led to European conquest (more or less) of the entire globe. I can't say for sure that the sun never setting on the English language is a result of vowels, but they are at least consistent with each other.

Vowels also allow a certain irrationality, as (in English), the vowel shown in a spelling has little real connection with the sound produced (e.g., try rhyming dough {doe}, cough {kof}, through {threw}, hough {hok}, lough {lahk}, sough {sef}, and bough {bau}; see also ought {ot}). It forces a sort of mental expansion, a realization that the things that we are told do not entirely line up with reality, but that neither is reason to disrespect and disregard them nor is it reason to bind ourselves to it. We still say our words how we want, and only loosely tie them to the vowels we see. This use of the old while constantly reexamining it and using only what is expedient is representative of the post-Harvey scientific world; it is probably no mistake that spellings were standardized shortly before we were able to turn our knowledge into heavy industry - a use of combined wisdom, acceptance of the unknown, and mental path of least resistance.

Spoken vowels are the primary means by which local pronunciations are formed; written vowels, therefore provide unity despite differences. This "you may say it your way, and I mine, but we're both English," attitude may not have led to democracy without a lot of other help, but it does at least constantly force us to recognize the finitude of our own knowledge, consider what things are right in an absolute sense and what are only relative and defined by man; in essence, a sort of micro-philosophy of itself.

Colonialism, industrialization, democracy, and postmodern philosophy all because of vowels? Perhaps not in any direct causal link, but the ideas seem to have been there waiting to be realized.