Secular art came into its own during this period with the rise of cities, foundation of universities, increase in trade, the establishment of a money-based economy and the creation of a bourgeois class who could afford to patronize the arts and commission works resulting in a proliferation of paintings and illuminated manuscripts. Increased literacy and a growing body of secular vernacular literature encouraged the representation of secular themes in art. With the growth of cities, trade guilds were formed and artists were often required to be members of a painters' guild. As a result, because of better record keeping, more artists are known to us by name in this period than any previous; some artists were even so bold as to sign their names.