This essays builds on the notion of “critical moments in learning” to suggest that teachers often teach without knowing it and that regardless of how much they publish, their greatest contribution is more likely to be in the lasting impact they have on their students' lives. In doing so, the author reflects on critical learning moments in his own education and, in turn, ponders how actions he had taken in and out of the classroom may have unwittingly influenced the thoughts, feelings, and, sometimes, even lives of the many students who had enrolled in his courses.