Islam in the West is not a book about belief. It is a book about behaviour, institutions, and the conditions under which plural societies either hold together or quietly come apart. Public debate on Islam in Western countries has become trapped between two failures of reasoning. One reduces a global faith and its followers to a single threatening essence. The other dissolves real tensions into comforting abstractions that leave individuals exposed and institutions unprepared. Both generate heat. Neither produces clarity. This book offers a different approach. Drawing on sociology, criminology, political theory, and institutional analysis, Paul O'Neill introduces a disciplined framework for understanding how Muslim life actually operates within Western civic systems. Rather than treating Muslims as a monolithic group, the book distinguishes between patterns of engagement based on observable behaviour, not belief. Cultural inheritance, ethical piety, traditional doctrinal life, and activated orthodoxy are examined as distinct modes, each with different implications for coexistence and public order. Crucially, the book separates everyday religious life from the rare but consequential moments when doctrine seeks authority beyond consent. It shows why most Muslims live ordinary, law-abiding lives once socioeconomic factors are accounted for, while also explaining why denial of doctrinal activation leaves societies vulnerable to coercion and ideological violence. Beyond diagnosis, Islam in the West addresses practical realities. It distinguishes socioeconomic crime from ideological violence, redefines integration as behavioural participation rather than cultural convergence, and examines how Western institutions themselves shape outcomes through clarity or inconsistency. It also specifies the protections required for individuals trapped in coercive environments without turning entire communities into suspects. The book concludes with a disciplined model of coexistence built on two commitments: allowing non-activated religious life to flourish under ordinary civic rules, and containing activated doctrine the moment it claims public authority. Success, it argues, looks ordinary.