I don't have an official link to point towards or anything, but there's this blurb from the 1.0 website linked on Gamerescape:

http://ffxiv.gamerescape.com/wiki/Armoury

Simply put, Adventurers in the realm of Eorzea are versatile enough to take on many of the tasks that everyday people do (gathering, crafting) as well as having the capability of learning the various martial arts found in Eorzea. (Disciples of War/Magic) At least it's not so far fetched in ARR that Adventurers can do all of these different things as you have a guide along the way (usually the Guildmaster) during the various class and job quests. In 1.0 the class quests were more or less designed as mini scenarios and really taught you nothing about your trade.