In 1978, Robert Brustein observed that Ibsen's The Master Builder subtly undermined the tenets of naturalism for which both the play and its author are usually remembered. Here, William W. Demastes suggests that, though lacking precise paradigms when they wrote the play and the critique, Ibsen and Brustein both approach the understanding of human interaction in ways that are currently explained through the ‘new’ scientific paradigm of chaos theory. This essay presents a general summary of chaos theory, applies it to The Master Builder, suggests ways in which Ibsen anticipates the postmodernists, and how, in turn, chaos theory can help in comprehending several paths that the theatre has followed since the inception of postmodernism. William W. Demastes is associate professor of English at Louisiana State University, and is author of Beyond Naturalism: a New Realism in American Theatre (1988). This essay is an extension of his book, and is designed in part as in introduction to his next book-length study, on the confluence of scientific and dramatic thought in the twentieth century.