Thieves also have many tools at their disposal to get out of sticky situations in the game. Not only do they possess the highest Evasion rating in the game, but they also have abilities such as Flee and Hide, which allow them to escape most dangers unharmed. Additional abilities such as Steal, Mug, Gilfinder, and Treasure Hunter, as well as their unique ability to pick Treasure Chests and Treasure Coffers with their thief's tools, makes the Thief the optimal choice for acquiring gil and items.

http://wiki.ffxiclopedia.org/wiki/Thief