The contrast between the class of the aristocrats or knights distinguished by a military lifestyle and wealth based in land, and the class of the rich craftsmen and merchants, produced a chronic instability in the city institutions. The nobility, derived from feudal aristocracy, lost its authority in municipal politics during the mid-thirteenth century to the emerging bourgeois class of cloth merchants and bankers, the officers of the well-organized arti maggiori (upper guilds). Inside the popolo of the guilds there were wealthy judges, rich notaries, moneychangers, doctors as well as spice merchants, wool and silk workers, blacksmiths or bakers.