His research focuses on developing complex systems concepts and applying them to diverse areas of scientific inquiry and to major social problems. He has worked on fundamental properties of evolution and learning, the evolutionary origins of altruism and collective behaviours, the relationship between observations at different scales, the relationship of structure and function, information as a physical quantity, and quantitative properties of the complexity of real systems. Applications have been to social, biological and physical systems.
His textbook Dynamics of Complex Systems, published in 1997 by Perseus Press, provides a wide-ranging perspective on the understanding of complex systems. His popular book Making Things Work describes the use of complex systems science for solving problems in military, healthcare, education, systems engineering, international development, and ethnic violence.