Pattern Theory is a groundbreaking exploration of the concept of pattern across a range of disciplines, including science, neuroscience, psychology, and social sciences. This book examines the meaning and implications of pattern, presenting a comprehensive body of theory that unifies concepts of form, order, and regularity and connects them to memory and perception. By challenging existing orthodoxies and linking evidence from brain and mind function, it outlines a robust theoretical framework around pattern searching and matching, pattern activation, and the continuity of pattern nexuses. This in-depth study of pattern theory and pattern thinking delves into the cognitive basis of patterns, their impact on reasoning and learning, and the social and collaborative nature of pattern recognition, expression, and representation. It also addresses philosophical issues and implications surrounding shared pattern thinking and introduces a broad conceptual basis for "pattern inquiry", providing a range of questions and methodologies for applying pattern theory. The book culminates in a manifesto for pattern theory and its application in pattern inquiry, offering 50 key principles that can be applied across various settings. Researchers, scholars, and practitioners are encouraged to explore and critique this unified theory as a lens for examining social and cognitive phenomena. Ideal for academics and professionals seeking to challenge their understanding of the connections between mind and society, as well as for those looking to deepen their understanding of pattern as a cognitive phenomenon, as a theoretical lens, and as a meta-methodology for inquiry, this text provides a substantive foundation for ongoing development and application of pattern science across multiple fields.