Calderón's most famous play, La vida es sueño (Life is a dream), explores the conflict between free will and predestination. It tells the story of the King of Poland who imprisons his son in a tower from birth in order to protect his reign and thwart the predictions of astrologers who saw the boy taking his father's throne. After several years, the King has a change of heart and orders his son drugged and brought to his palace for a trial. The young man behaves so badly, however, that the King soon banishes him back to his prison. Waking up in the tower, the son is soon convinced that he never left his lonely prison, that the entire trial was just a dream. But a peasant uprising soon liberates the confused prisoner once more and results in the boy being crowned King. Fearful of waking once more in the tower and learning that this new life is but a dream, this time he conducts himself with discretion.

This monologue is the most important one in the play and one of the best known ones in the history of Spanish theatre.

Born in Madrid, Spain, on January 17, 1600, Pedro Calderón de la Barca would eventually become one of Spain's most important dramatists. Along with the older playwright Lope de Vega, Calderón would dominate Spain's Golden Age of theatre.

Educated at the Jesuit Colegio Imperial, Calderón studied law at the University of Alcalá (1614-15) and the University of Salamanca (1615-21), but did not earn a degree. In 1621, he entered the household of the Constable of Castille, Don Bernardino Fernández de Velasco. Two years later, in 1623, he began writing plays for the court.

Calderón became a priest in 1651, but continued to write plays as the court dramatist for Philip IV. He also wrote two autos sacramentales each year for the city of Madrid. In his later years, he developed a series of elaborate mythological themes that reflected the tastes and interests of the Spanish Court during the waning years of the Golden Age. He died in Madrid on May 25, 1681. Of his 120 surviving works, approximately 80 are autos sacramentales, morality plays celebrating the mystery of the eucharist on Corpus Christi day.