How can we objectively define categories of truth in scientific thinking? How can we reliably measure the results of research? In this ground-breaking text, Dienes undertakes a comprehensive historical analysis of the dominant schools of thought, key theories and influential thinkers that have progressed the foundational principles and characteristics that typify scientific research methodology today. This book delivers a masterfully simple, 'though not simplistic', introduction to the core arguments surrounding Popper, Kuhn and Lakatos, Fisher and Royall, Neyman and Pearson and Bayes. Subsequently, this book clarifies the prevalent misconceptions that surround such theoretical perspectives in psychology today, providing an especially accessible critique for student readers. This book launches an informative inquiry into the methods by which psychologists throughout history have arrived at the conclusions of research, equipping readers with the knowledge to accurately design and evaluate their own research and gain confidence in critiquing results in psychology research. Particular attention is given to understanding methods of measuring the falsifiability of statements, probabilities and the differing views on statistical inference. An illuminating book for any undergraduate psychology student taking courses in critical thinking, research methods, BPS's core area 'conceptual and historical issues' as well as those studying masters, phd's and experienced researchers.