Economics arguably has the strongest influence on policy making among all the sciences, but it has been notoriously difficult to integrate other relevant disciplines like ecology and psychology into economics. Is this because economists value money more than nature unlike ecologists or glorify human rationality unlike psychologists? Instead of speculating on economists' values and views, this project aims to (1) identify distinctive methods and concepts that economists rely on in their practice; and (2) assess whether and how these can be effectively modified to take insights from the other disciplines. The project achieves these goals by a unique combination of (A) an interview-based qualitative study of interdisciplinary projects involving economists and (B) a careful methodological analysis based on the philosophy of science. The findings will be used to form a practical guide to interdisciplinary research for economists and their collaborators, as well as for science policy makers.