This 1941 essay was published in the second volume of Heidegger’s interpretation of Friedrich Nietzsche. It is a presentation of the decisive moments in the history of metaphysics, which begins with the distinction between essentia, what an entity is, and existentia, that an entity is. This distinction arises from the concealment of beyng, which marks the origin of metaphysics. Heidegger reduces the distinction between essentia and existentia to its Greek origin. He shows how the Aristotelian concept of ἐνέργεια becomes actuality or the work of causes. He also explains the transformation of truth into certitude and of ὑποκείμενον into subject.
The second part is an interpretation of the relation between actuality and subjectivity in the philosophy of Gottfried Wilhelm Leibniz. For Leibniz, every entity as an entity is either a subject or a monad. The monad is determined by representation in its double meaning of perceptio and appetitus. The “perception” signifies any interior spontaneous expression or representation of the universe. The appetitus is the tendency of the monad to pass from one perception to the other in quest of a more and more adequate perception of the universe. Both are types of presentation or proposing: perceptio represents the universe; appetitus proposes the perfection of life toward which the monad strives. In his 24 metaphysical theses, Leibniz says that there is a reason in nature why something exists rather than nothing. This ground is God as the necessary entity, which causes the being of all other entities.
In the third part, Heidegger explains the difference between subjectivity and subjectity. Since René Descartes grounded the being of entities on the self-certain subject, every entity has become either an object or a subject as that which objectifies. Heidegger calls this subject reference of all being subjectity, which constitutes both the objectivity of objects and the subjectivity of subjects.
The fourth and final part contains the 24 metaphysical theses of Leibniz, which Heidegger considers to be the highlight of his metaphysics.