What is the nature of spacetime


Esfeld's "Metaphysics of Nature"


The German philosopher who teaches in Lausanne develops a “metaphysics of nature” Michael Esfeld in his book


Esfeld, Michael: Natural philosophy as a metaphysics of nature. 218 pp., Kt., € 10.—, 2008, Suhrkamp, ​​Frankfurt


In his metaphysics, however, it is not about something that is assumed to exist beyond the empirical world, such as a final principle, but about a “coherent and complete theory of the empirical world itself.” “Complete” means that it there is nothing that is not covered by the terms of this theory, “coherent” means that the terms with which this theory works are related to one another. Metaphysics is thus the attempt to bring together the knowledge we gain through the various sciences into a coherent and complete view of the world, including ourselves. Metaphysics is therefore neither a priori nor does it lead to unshakable knowledge. Rather, it is just as hypothetical as the sciences.


Esfeld's metaphysics is based on scientific realism, which is characterized by the three assertions:


¢ The existence and nature of the world are independent of scientific theories.


The nature of the world determines which scientific theories are true.

In principle, the sciences are able to give us cognitive access to the nature of the world.


For Esfeld there is no fundamental limit to the knowledge of the world, and in the history of the sciences he sees a history of progress in the discovery of the nature of the world.


Esfeld's metaphysics is also a holism with coherence as a strong pillar: On the basis of observational statements that are caused by experience, we try to construct a coherent system of scientific statements. Coherence means that the theoretical statements not only do not contradict each other, but that their conceptual content is as closely related as possible. When two rival theories agree in their experimental predictions, which of the two theories fits better into an overall coherent system of our knowledge of the world?


With this set of instruments, Esfelds developed a differentiated analysis of the two great physical theories of the 20th century, the relativity theory and the quantum theory. Then the special and general relativity theory fix us on the metaphysics of a four-dimensional block universe, the content of which is formed by four-dimensional events and processes. The thesis of the block universe says that the four-dimensional space-time with all its content simply exists. Existence is not relative to a mode of time (past, present, future) because there is no global, objective temporal order of all events in the universe; because there is no universally preferred reference or coordinate system. Esfeld advocates, on the basis of the theory of relativity, expanding the thesis of the world as a block universe in such a way that four-dimensional events and processes form its content and there are therefore no three-dimensional substances that remain as a whole for a while. This thesis is with the













Michael Esfeld


Assumption of a time direction and compatible with time-directed, irreversible processes. The question of the relationship between the metric properties that characterize spacetime and the properties of non-gravitational energy is open. In current research there is a dualism between spacetime with the metric field on the one hand and the fields of non-gravitational energy-matter on the other. This dualism reflects the dualism between general relativity and quantum field theory. A unification - or overcoming - of both theories through a unified fundamental physical theory has not yet succeeded. The focus of the research is in the direction of a quantum theory of gravity. But in principle the two monistic positions, either the matter to be traced back to space-time or the space-time to be traced back to matter, are still justifiable natural-philosophical positions. But there are central arguments against both positions: All previously available philosophical descriptions are dependent on the reference to space-time. Conversely, one can show that space-time only exists together with the metric field. Hence, space-time itself has a material character in that it includes gravitational energy. On the one hand, spacetime itself is substantial as a whole, but on the other hand it is also relational because it is in metric relations between spacetime points. But it is still too early to make philosophical speculations about how the metaphysics of space-time and matter could be presented in connection with a unified fundamental physical theory. Nevertheless, both theories agree on one position in natural philosophy: that of structural realism. It is structural realism as a metaphysical thesis that Esfeld shows that we can in principle fully recognize nature.


A structure is a network of concrete physical relations between objects. Structural realism is realism in relation to concrete physical structures. According to Esfeld's structural realism, ontologically, structures in the sense of concrete physical relations are everything there is in the field of fundamental physics. Structures (relations) and objects are ontologically on the same level and are mutually dependent on one another. Structures exist as concrete relations between objects, and these relations are constitutive properties for the objects that are in the relations. Nothing can be a space-time point without being in metric relations, and nothing can be a quantum object without possessing time-dependent properties that are subject to the state entanglements. The time-dependent properties as well as the metric properties belong to the properties that are constitutive for a quantum object or a point in time.


The points of space-time exist exclusively in the metric relations in which they stand. Likewise, the properties of non-gravitational energy-matter, which are dealt with by quantum physics, are not intrinsic properties, but originally exist in relations of the entanglement of states.