To this concept of 'poor theatre' Jerzy Grotowski (an atheist) added the concept of the 'priesthood' or sacredness of the actor. When the actor entered the sanctity of the performance space, then a special event occurred, much like the Mass in the Catholic Church. It was in this space, in the holy relationship between the actor and the audience, that an audience was challenged to think and be transformed by theatre. In this sense, Jerzy Grotowski was one of the key figures in the development of political theatre in the 20th Century. His theatrical productions often contained political and social themes. The actor, depending only on the natural gifts of voice and body, could bring the sacred rituals of theatre and the themes of social transformation to the audience. The audience became pivotal to theatrical performance, and theatre became more than entertainment: it became a pathway to understanding.