This chapter picks up the historical story in the middle of the twentieth century. Against a background of an enhanced sense of independence and confidence of people and institutions that developed following World War I and World War II, I argue that it was in the middle of the twentieth century, from the 1930s to 1960s, that Australian criminal law came into its own – measured in terms of an orientation around national coordinates, and in the self-confidence of its practitioners and academics. I demonstrate that, with close reference to the decisions of English courts, and commentaries such as that of Glanville Williams – and, increasingly over the period, to US developments like the Model Penal Code – Australian lawyers and commentators came to forge an independent path for the criminal law in the mid-century. Working over and above developments that occurred within state jurisdictions, and across code and common law modes of criminal law, practitioners and scholars were thoroughly engaged in a global debate about the development and improvement of the law of crime, and in a complex and subtle negotiation between what Australia shared with others, and what might be thought mark it out. In the mid-century, it became possible to think about Australian criminal law as such, to conceptualise Australian criminal law as a meaningful idea.