Collected here for the first time, this series of lectures delivered by Lonergan at Boston College in 1957 illustrates a pivotal time in Lonergan's intellectual history, marking both the transition from the faculty psychology still present in his work Insight to intentionality analysis and his initial differentiation of the existential level of consciousness. The lectures on logic deal with the general character of mathematical logic and its relation to truth, Scholasticism, and Aristotelian logic. Continuing Lonergan's long-standing interest in the foundations of thought, the lectures on existentialism offer a penetrating account of Husserl and his influence. They also deal with Jaspers, Heidegger, Sartre, and Marcel. They offer reflections on such topics as being oneself, dread, horizon, and the existential gap. Perhaps more dramatically than in any other work these papers reveal Lonergan's dual commitment to the rigor of scientific analysis (in the field of mathematical logic) and to the sensitivity of continental philosophies to existential issues.