In this interview, David Zierler, Oral Historian for AIP, interviews Marshall Baker, professor of physics emeritus at the University of Washington. He recounts his childhood in Salem, Massachusetts, and he describes his undergraduate experience at Harvard, where he majored in physics. Baker describes the formative influence of Julian Schwinger, and he discusses his first year of graduate school at Caltech, where he studied with Richard Feynman and Frederik Zachariasen. He explains his motivation to return to Harvard to complete his graduate research under Schwinger on the interactions of mesons and nucleons at low energy. Baker discusses his postdoctoral research at Stanford to be the house theorist for the Stanford Linear Accelerator and his collaborations with Shelly Glashow and Charlie Sommerfield. He describes his work as a junior faculty member at Stanford and the enjoyment he felt teaching quantum field theory as a student of both Feynman and Schwinger. Baker explains his decision to join the faculty at the University of Washington where he worked closely with Ken Johnson on quantum electrodynamics. Baker explains that his hire was part of a broader effort by the department to improve in elementary particle physics, and he describes the broader advances in the field during the 1960s in understanding hyperons and mesons and S-matrix theory. He explains the value of his collaborations with Soviet physicists and the significance of Gell-Manns quark model. Baker discusses his collaborations in the mid-1980s with Zachariasen on finding nonperturbative solutions for the gluon propagator which led to an approximate solution of QCD, he explains how a theoretical problem can take 15 years to solve and why the feedback mechanisms for success are more difficult to ascertain than is true in experimentation. Baker discusses his interest in string theory and Bari measurements in the years leading up to his retirement, and he explains why he remains hopeful that this research will yield fundamental understanding about the part of the field between a quark and an antiquark that produces the confining force. At the end of the interview, Baker emphasizes the importance of always staying in learning mode, because discovery in theory requires openness always to new fields of inquiry.