William Shakespeare (1564-1616) was a playwrite in England.  The Merchant of Veniceis one of his many "comedies." Some scholars however, have made the argument that the play is one of his tragedies.  Other tragedies of Shakespeare include Hamlet and Romeo and Juliet.  Shakespeare lived in a time when Jews had been expelled from England for over three centuries.  However, as a playwrite, Shakespeare also probably faced much prejudice and hatred-theater was banned from his home town of London during his lifetime and so the theaters had to move outside of the city walls.  This situation may have made him sypathetic to the plight of Jews, hence the play as a work of tragedy. 

Shakespeare married a woman named Anne Whateley, but he may have also had a male lover during his lifetime-a practice not uncommon for men of his era.  Many of his sonnets suggest the possibility of this.  Shakespeare's comedies, performed at the Globe theater, were played to an audience which included as many peasants as it did nobles and loyalty, and so the comedy appeals to this lower class as well.  Shakespeare's works are full of political humor, but also run rampant with sexual and scatalogical humor. 

Shakespeare lived during the reign of Queen Elizabeth who had a man in her service who she cared for deeply (she never married during her reign, but was rumored to have lovers) and who was rumored to be a Jew.  If this had been the case, Shakespeare's play would have to have been sensitive to her favor.  Hence, more evidence of the play as a tragedy. 

In Shakespeare's time, it was the common practice for men to play the parts of women in most productions.  For this reason, there is a double joke in the gender switch which Portia and Nerissa undergo.  They would have been men dressed up as women who then "disguise" themselves as men.  Such humor would not have been lost on contemporary audiences and was probably the reason behind the inclusion of the disguises.