This book adopts an integrated history and philosophy of science approach to consider the historical origins and methodological pitfalls of field experiments in economics. It explains key concepts such as control and randomization and identifies two distinct origins of field experimentation in economics: controlled laboratory experiments and randomized field trials. Careful historical analysis reveals that two strands of field experiments have developed, with rather different methodological rationales regarding the validity, both internal and external, of inferences about experimental results. The authors propose a unified methodological framework that makes explicit the complementarity between the two strands of field experiments, as well as between experimentation and other research methods such as econometrics. In addition, the methodological framework aims not only to bridge both strands but also to make explicit often-assumed ethical and political values in experimental design and practice in the field. This book will be valuable reading for advanced students and scholars in the history of economics, philosophy of economics, economic methodology, and experimental economics. The Open Access version of this book, available at www.taylorfrancis.com, has been made available under a Creative Commons Attribution-Non Commercial-No Derivatives (CC-BY-NC-ND) 4.0 license.