The topic of the seminars was Heidegger's ontology and phenomenology as it pertained to the theory and praxis of medicine, psychology, psychiatry and psychotherapy.
During active military duty as a field doctor during World War II (which "all Swiss men who were not psychologically impaired were required to do"), Boss read Heidegger's dense and often complicated text, Being and Time.
Yet, as a psychiatrist, Boss was captivated by the ideas, which he evaluated as "fundamentally new, unheard of insights into the human being's way of existing in the world", and was intrigued by the author.
Heidegger included in his introductory lecture a brief explication of Da-sein, "the basic constitution of human being" as "being-in-the-world".
He also offered to the students a radical diversion from conventional Cartesian epistemology, namely "all objectifying representations of a capsule-like psyche, subject, person, ego or consciousness in psychology and psychopathology must be abandoned in favor of a new understanding."
He likened Heidegger's attempt to discuss his philosophy with medically trained doctors and students "as if a man from Mars were visiting a group of earth-dwellers and trying to communicate with them."
Yet, Boss was consistently sympathetic to Heidegger's task, which he described as "Sisyphean, of "giving my friends, colleagues, and students a sound philosophical foundation for the medical practice."
Neither Heidegger nor the seminar students "grew tired" of the material and worked to "achieve a common ground" in their thinking.
Boss observed that with his "conscience as a doctor" he could no longer expect Heidegger, growing in age and declining in physical ability, to prepare and participate in the seminars.
In one of his last documented letters (dated 21 February 1971), Heidegger congratulated Boss on an award granted him by the American Psychological Association.
Heidegger died in 1976, though before his death he contributed to and edited Boss's text Existential Foundations of Medicine and Psychology, published in 1979.