In one of his last publications, "Recent Considerations in Daseinsanalysis," Boss discussed the significance of Heidegger's conception of Ereignis for psychology and an understanding of psychotherapy. Ereignis, the Event of Appropriation, is the coming together, the belonging together of being's presencing and human revealing. It is the ongoing happening of Dasein as the realm of the presencing of being. In Ereignis, being and human beings are mutually appropriated in that the "there" of Dasein's disclosive engagement is granted by the presencing of being, just as Dasein's disclosive engagement preserves the "there" of being among beings. In Medard Boss' words: "Ereignis is the invisible unity of the appeal of being and of Dasein's response to this appeal".
Lest we misconstrue Ereignis as a factual occurrence set in linear time, we need appreciate the character of Heidegger's formulation. Ereignis is a relational and dynamic understanding as opposed to a reified and static concept. It is an imaging of the origin of Dasein as continuously occurring, concurring with the advent of the world. It is not a primal origin, set once upon a time, but the perpetual happening of Dasein's being called into its existing, its being called upon to be. Being, as understood in Ereignis, is no-thing--not a thing whose presence Dasein is set upon revealing. Instead it is the dynamic coming-into-presence which sets forth any and all things as present before us, the coming-into-presence which prevails upon us to preserve what has been presented. Joseph Kockelmans observes that "[i]n each concrete case, the appropriating event binds together Being and beings; it weaves Being, man, things, and world together into an articulated and textured whole". The Event gives us not a metaphysics of presence, but a mystery whose unfolding is the heart of our worldly existing.
"Heidegger," writes Boss,
considered Ereignis his deepest insight and, when you think about it, you begin to see this relationship between Being and Da-sein not only makes psychotherapy possible in the first place, but also gives its most fundamental purpose, that is, for the therapist to respond to the appeal of the patient to be.What calls for the analyst's response is the patient's own being called forth to be, her or his own being as called on by being. "The healing response," as Boss explains elsewhere, "of the analyst to the appealing address of the patient is to enable him to appropriate as his own the innate potentials which up until treatment had been hidden, disturbed, or distorted". The concern of the therapy is the patient's potentiality-for-being, which whether taken up explicitly or tacitly always remains at issue for them.