Preface introduces reader to the general context of Heidegger's philosophy and its application to psychiatry. It situates Heidegger's thought in the epistemological scheme outlined by Foucault in his Les mots et les choses. In the context of the so-called modern episteme, what becomes visible are not only contours of the ontological analysis of human existence, but also its limitations. One of these limitations is the impossibility to grasp the end of human existence and the disintegration of the self as positive phenomena, i.e. to see them in themselves, and not only in the light of the individual unity of human existence, which has consequences especially for psychiatric approach to schizophrenia. In order to overcome this limitation, Deleuze's and Guattari's schizoanalysis is placed in opposition to the ontological analysis of human existence.