Naturalism is a movement in European drama and theatre that developed in the late 19th and early 20th centuries. It refers to theatre that attempts to create a perfect illusion of reality through a range of dramatic and theatrical strategies: detailed, three-dimensional settings (which bring Darwinian understandings of the determining role of the environment into the staging of human drama); everyday speech forms (prose over poetry); a secular world-view (no ghosts, spirits or gods intervening in the human action); an exclusive focus on subjects that are contemporary and indigenous (no exotic, otherworldly or fantastic locales, nor historical or mythic time-periods); an extension of the social range of characters portrayed (away from the aristocrats of classical drama, towards bourgeois and eventually working-class protagonists); and a style of acting that attempts to recreate the impression of reality (often by seeking complete identification with the role, understood in terms of its ‘given circumstances’, which, again, transcribe Darwinian motifs into performance, as advocated by Stanislavski). Naturalistic role play is used within theatrical performances to demonstrate to the audience or show the audience how this would appear in real life. No still images are used as this does not show the full quality of the piece of drama. Naturalism was first advocated explicitly by Émile Zola in his 1880 essay entitled Naturalism on the Stage.
Australian Catholic University Useful discussion on realism and naturalism in the theatre, the differences between the two and the position of Ibsen’s A Doll’s House..
San Diego Opera (Archived version) Outstanding article clearly explaining Zola’s naturalism with the aid of extracts from two of his works. This is just about the only place on the Web where you’ll find the appropriate excerpts about naturalism from Zola’s two famous sources – the preface to Thérèse Raquin and The Experimental Novel.