<P> I hold the world but as the world, Gratiano; A stage where every man must play a part, And mine a sad one . </P> <P> In his work The Praise of Folly, first printed in 1511, Renaissance humanist Erasmus asks, "For what else is the life of man but a kind of play in which men in various costumes perform until the director motions them off the stage ." </P> <P> Likewise the division of human life into a series of ages was a commonplace of art and literature, which Shakespeare would have expected his audiences to recognize . The number of ages varied: three and four being the most common among ancient writers such as Aristotle . The concept of seven ages derives from medieval philosophy, which constructed groups of seven, as in the seven deadly sins, for theological reasons . The seven ages model dates from the 12th century . King Henry V had a tapestry illustrating the seven ages of man . </P> <P> According to T.W. Baldwin, Shakespeare's version of the concept of the ages of man is based primarily upon Palingenius' book Zodiacus Vitae, a school text he would have studied at the Stratford Grammar School, which also enumerates stages of human life . He also takes elements from Ovid and other sources known to him . </P>

All the world's a stage merchant of venice