Preview: "Top-Down Cosmology and Model-Dependent Realism. A Philosophical Study of the Cosmology of Stephen Hawking and Thomas Hertog"

Doctor in philosophy and moral sciences (VUB).

Title of my dissertation: Top-Down Cosmology and Model-Dependent Realism. A Philosophical Study of the Cosmology of Stephen Hawking and Thomas Hertog, Uitgeverij VUBPRESS Brussels University Press, 2021.

dr.. Alexander François van Biezen

Supervisor: prof. dr. Gustaaf C. Cornelis.

Popular-scientific abstract

Within the domain of history and philosophy of cosmology, I investigated the cosmological work of Stephen Hawking — the famous British scientist in a wheelchair — and Thomas Hertog — his Flemish disciple — between 2006 and 2018. In 2006, Hawking and Hertog put forward a new framework called top-down cosmology. This approach starts from the present (“at the top”), with the properties of the universe as we can observe it today, and works its way back to the past (“down to the bottom”). This framework views the origin of the universe as all possible histories layered on top of each other. The universe did not have a single, unique beginning. Instead, it began in about every possible way.

What makes top-down cosmology stand out, compared to many other competing approaches, is Hawking’s attempt to scaffold his cosmological work by means of his philosophy of model-dependent realism. Scientific realism holds that our best scientific theories are approximately true and that the unobservable objects they refer to really exist. Hawking claims it is meaningless to ask whether a theory is real, only whether it agrees with observation. When two competing, even mutually incompatible, theories agree with observation, it is impossible to say one is more real than the other. From a philosophical point of view, model-dependent realism is seriously flawed, because it is insufficiently worked out with regard to modern model theory and self-refuting as a philosophical claim (as Hawking dismissed philosophy altogether). However, from a cosmological point of view, it gave Hawking and Hertog a practically unconstrained liberty to play with concepts and tools of different branches of physics needed to construct their cosmological models.

            To find out whether model-dependent realism is just a brazen and failed attempt at philosophising or a brilliant strategic move with solving a fundamental cosmological problem in mind, I examined the relationship between top-down cosmology and model-dependent realism from different angles. I have come to the conclusion that, when viewed from a broader perspective, Hawking’s and Hertog’s approach in cosmology is indicative for a gradually changing attitude within the scientific community of fundamental physics and cosmology about what counts as “the scientific method”. Traditionally, a theory was regarded as scientific when it made predictions which could be falsified through experiment or observation. However, recent decades gave rise to physical theories like string theory whose predictions lie way beyond the reach of what is currently technically possible. Top-down cosmology fits in with this growing trend of a more lenient view towards falsifiability of a theory and a stronger focus on the conceptual characteristics of a theory (like simplicity, elegance, range, internal and external consistency) to evaluate its viability.