What is the role of Jaques in Shakespeare's As You Like It, and why is he important to the plot of the play?

Jaques is one of the main characters in the Shakespeare play As You Like It. He is one of Duke Senior's noblemen who lives with him in the Forest of Arden. Jaques' role in the play is centered more on observation and commentary than action; he provides witty criticism and serves as a negative foil to the happier residents of the Forest of Arden. He also delivers one of Shakespeare's most famous monologues, beginning with "All the world's a stage," which philosophizes about the inevitability of aging and death. Jaques' attitude and worldview stand in sharp contrast to the other characters in the play, who enjoy living in the Forest of Arden; he spends much of the play dwelling on the hardships of life, and frequently criticizes those around him. He is important in the story not because of his actions, because he actually does very little; he is significant to the play primarily because of his role as a pessimistic foil to the other characters.