In this lecture on the grounding of the world picture of modernity through metaphysics, delivered in Freiburg on 9 June 1938, Heidegger claims that modernity is the age of the world as “picture” and explains how the world becomes “framed” in this way. Every age is grounded through its metaphysics, which determines the being of entities and the experience of truth. Every new age starts with a metaphysical revolution. At the beginning of his lecture, Heidegger describes five fundamental phenomena of modern times: (1) modern science, (2) machination and technology, (3) the nature of art as lived experience, (4) the realization of values in culture, and (5) the “de-godding” (Entgötterung), that is, the flight and disappearance of the gods. In his lecture, Heidegger only discusses modern science and the metaphysical revolution that made it possible.
Modern science is essentially research and, as such, is dominated by method. It limits itself to specific regions of entities that are grounded in characteristic features of reality, for example movement, and each are studied with specific methods. Because modern science limits itself to method, it can achieve levels of strictness and exactness that were unthinkable to Greek ἐπιστήμη and medieval doctrina et scientia. In his own little corner, every researcher follows the method of his science as strictly and exactly as possible. Modern science has been institutionalized and has thus become business. The metaphysical foundation of modern science is the objectification of entities, which in turn is grounded through method. Modern science no longer concerns itself with the being of entities, but only with objects. How did entities become objects? This transformation is only possible when entities are no longer disclosed in their being, but represented by subjects. An entity is only an entity if a subject perceives it. Truth can then no longer be ἀλήθεια, the unconcealment of entities in their being; it becomes the certitude of representations.
René Descartes was the first philosopher to determine the being of entities as representations and truth as certitude. The scientific revolution of modernity is at the same time a metaphysical change in what it means “to be” human. Human beings became subject and, as subjectivity, the foundation of all entities in their being and truth. The world as the whole of entities became a representation or picture. Modernity is the age of the world picture.