What is the theme in Brecht on Theatre: The Development of an Aesthetic by Bertolt Brecht?

Another theme is Theory and practice. Brecht was both a theoretician (in that he thought through and carefully developed a set of beliefs and a process by which they could be manifested) and a practitioner (in that he actually applied his beliefs and theories to the work that he was doing). In other words, he practiced the socialism he preached, and urged others (theatre practitioners and general workers alike) to do the same. It's important to note, however, that the writings in this collection indicate quite clearly that his commitment to both evolved over the years.