Michele Longo's 1906 treatise represents one of the earliest systematic Italian attempts to build a science of criminal psychology. Writing at a moment when psychology was still forging its identity as a discipline separate from philosophy and law, Longo sought to consolidate scattered theories about why people commit crimes into a coherent framework. He argues that understanding criminal behavior requires examining the dynamic tension between individual psychological tendencies and the expectations of society. The book moves from foundational principles of criminal psychology through environmental influences on criminal conduct, culminating in detailed analyses of specific criminal acts. Longo's work reflects the optimism of early psychological science, which believed human behavior could be classified, measured, and ultimately predicted. Today, the text serves less as a practical guide than as a fascinating historical document, revealing both the prescient intuitions and the dated assumptions of turn-of-the-century criminological thought.
