of the Zollikon Seminars was held in July, 1969. 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. Boss and Heidegger agreed to continue corresponding via mail, and Boss visited Heidegger's home in Freiburg as both their schedules allowed. In one of his last documented letters (dated 21 February 1971), Heidegger congratulated Boss on an award granted him by the American Psychological Association. He also encouraged Boss to continue with many of the ideas discussed in the seminars and suggested several of his own texts, but also dissuaded Boss from reading any of "the literature on Heidegger". After that, Heidegger retired to his Black Forest cabin and "limited his visits and letters." 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. Boss died in 1990. Select passages 24 or 28 January 1964 Why can't there be something real that is not susceptible to exact measurement? Why not sorrow, for example? 2 November 1964 The basic character of nature represented by the natural sciences is conformity to law. Calculability is a consequence of this conformity to law. Of all that is, only that which is measurable and quantifiable is taken into account. 18 January 1965 The nature of being sick cannot be adequately grasped without a sufficient determination of being healthy...It is an ontological phenomenon, that is, it refers to a possibility of being and not merely to the logic of a propositional negation. 11 May 1965 But are the connections between psyche and soma something psychological, something somatic, or neither one or the other? We wind up in a dead end, which shows you better than anything else how essential the question of method is. 6 July 1965 In Greek and medieval thought, the concept of an object and of objectivity did not yet exist. Objectivity is a definite modification of the presence of things...Modern science rests on the transformation of the experience of the presence of beings into objectivity. 23 November 1965 Daseinanalysis is ontic. The analytic of Dasein is ontological. See also Zollikon Heidegger Gesamtausgabe HGA 9. Zollikoner Seminare, ed. Peter. Trawny, 2017, XXXII, 880p. References Heidegger, M. (2001). Zollikon Seminars. Protocols- Conversations-Letters. M. Boss (ed.). R. Askay & F. Mayr (trs.).