This book presents a theoretical critical appraisal of the Mechanistic Theory of Human Cognition (MTHC), which is one of the most popular major theories in the contemporary field of cognitive science. It analyses and evaluates whether MTHC provides a unifying account of human cognition and its explanation. The book presents a systematic investigation of the internal and external consistency of the theory, as well as a systematic comparison with other contemporary major theories in the field. In this sense, it provides a fresh look at more recent major theoretical debates in this area of scientific research and a rigorous analysis of one of its most central major theories. Rigorous theoretical work is integrated with objective consideration of relevant empirical evidence, making the discussions robust and clear. As a result, the book shows that MTHC provides a significant theoretical contribution for the field of cognitive science. The content is useful for those interested in theoretical and empirical issues concerning major theories in the contemporary field of cognitive science.