Our starting point in this article is that the question of the essence of psychotherapy has to some extent been neglected. Its medical context has strengthened the tendency to interpret psychotherapy in general from a technical and overtly rationalistic standpoint. Instead, we would underline the importance of the philosophical and historical roots of all psychotherapies. In our view, it is imperative to acknowledge the antirationalistic underpinnings that have always informed the discipline. We show how speculative mysticism and the late philosophy of Martin Heidegger have proved to be indispensable tools in setting psychotherapies in their philosophical and historical context. Robert Stolorow has also recently emphasised that Heidegger's philosophy in Time and Being can be used to both understand and develop thinking in psychotherapies. We find it surprising that Heidegger's late philosophy has not previously been considered a promising standpoint for theoretical research and show how Heidegger's concepts of twofold thinking and Gelassenheit are useful conceptual tools in understanding various dimensions of psychotherapies.