In Memoriam: John W. Addison, my PhD advisor

John W. Addison (1930–2026), a logic professor at UC Berkeley, is remembered by his former PhD student as an exceptional instructor whose precision, elegant notation, and ability to identify key techniques profoundly shaped the author's career. The author recounts how Addison's guidance—from a captivating logic course to a seminar on definability—led to a breakthrough using infinite games and analogical reasoning to solve an open problem about the complexity of point subsets in Baire Space.