This book provides a comprehensive study of the work of M. David Merrill, a major pioneer in the field of instructional design. This book centers on his research on his second generation instructional design (ID2) theory, Instructional Transaction Theory, and First Principles of Instruction, which has had a substantial impact on the instructional design field. It appealing to the instructional design research and practitioner-based communities who can draw on specific sections of this book to enhance their own work. It is also intended for those seeking to learn more about the relationship between the instructional design field, learning theory, curriculum studies, and lifelong learning/adult education studies. Through this critical, yet empathetic study of Merrill 50+ year research agenda, this book provides an illuminating field of entry into a broad range of topics, both those that are central to Merrill own research agenda, and into areas that extend well beyond his essentially cognitivist epistemological assumptions.