In his Leibniz lectures in the summer semester of 1928, Metaphysical Principles of Logic, Martin Heidegger touches on the “question of ethics”. Fundamental ontology as developed in Being and Time is not the whole of metaphysics. It has to be supplemented by a metontology. Only the unity of fundamental ontology (which encompasses the analysis of existence and the analysis of the temporality of being, the question of being proper) with metontology (which Heidegger likewise connects to the question concerning the totality of beings as well as the recoil of ontology onto existence, metontology being “also the domain of the metaphysics of existence”) provides the full concept of a possible metaphysics. Being needs human being, Dasein, as the locus where it strikes. Dasein is the place where being eventuates. “There is being only when Dasein understands being.” Dasein’s understanding of being is the condition of possibility for being at all. The question concerning the sense of being per se must be preceded by questioning the sense of the being of Dasein. It takes its starting-point from Dasein and it must return to this starting-point. Heidegger calls it an “inner necessity that ontology boomerang back to where it set out from”. This is the definition which Being and Time provides of philosophy as such: “Philosophy is universal phenomenological ontology proceeding from the hermeneutics of Dasein which, as the analysis of existence, has tied the end of the thread of all philosophical questioning to where it arises and to where it boomerangs back.” Without allowing itself to be reduced to an anthropology or an ontic Weltanschauung, fundamental ontology, including metontology, must boomerang back into concrete existence. As Heidegger will explain in the Letter on Humanism, existence is neither the “reality of the ego cogito” nor is it the “reality of the subjects who act with each other and for each other and so come to themselves”, but rather it is “ek-static dwelling close to being”.From this proximity a certain obligation or necessity for action in a possible authenticity can be derived. “Only those who understand this art of existing, of treating what has been individually grasped as what is simply unique for their actions, and at the same time are clear about the finiteness of this action understand finite existence and can hope to attain something in this existence. The art of existing is not self-reflection, which is an uninvolved hunt to dig up motives and complexes from which one gains reassurance and a dispensation from action; rather it is solely the clarity of action itself, the hunt for genuine possibilities.” The topic of metontology seems to imply an entire art of existing, as Heidegger says, and a theory of action, indeed, a kind of ethics which cannot be separated from the problem of a general ontology. Dasein is ethically distinguished from other beings by the fact that it always already understands being and from this understanding of being creates the possibility of explicitly accepting it and grounding it in an action or a deed. The ethicalness of Dasein which understands being is expressly characterized by Heidegger as “guardianship, that is, the care for being”. Care for itself (we recall that Dasein is that being which “in its being is concerned with its own being”) is inseparable from the ontological care for the truth of being as a whole. “As the ek-sisting being, the human being withstands Dasein by taking the Da as the clearing of being into its ‘care'”.