This book has re-examined criminal responsibility. In the context of Australian criminal laws, it reassessed the general story told about the rise to prominence of criminal responsibility from around the turn of the twentieth century, paying close and careful attention to the intricacies of developments in criminal responsibility within this period. At the same time, the book reconsidered the role and, hence, significance of criminal responsibility in criminal law, arguing that criminal responsibility organises keys sets of relations – between self, others and the state – as relations of responsibility, and that this is what makes it significant. My analysis generated two main insights. First, it revealed the gradual and distinctive way in which Australian criminal laws came to be organised around criminal responsibility over the twentieth century, and what this makes possible and what it precludes. Second, it exposed the complexity and dynamism of the relations of responsibility that subtend criminal responsibility principles and practices – substituting the still-dominant account of criminal responsibility as singular, general and universal, for an account characterised by multiplicity, specificity and variation across the criminal law field.