Plato’s Holographic Cave: String Theory and Spatial Dimensionality

Baptiste Le Bihan (University of Geneva)

How many dimensions does space have? Among metaphysicians, three-dimensionalists answer 'three' and four-dimensionalists 'four' by reducing time to a component of the four-dimensional spacetime. However, at first glance, string theory seems to suggest a different view, namely that space is structured by ten or eleven dimensions. 

Yet closer look at string theory and some aspects of black hole physics reveals a different story. In fact, assuming that string theory is on the right track, far from finding out that space is made up of more dimensions than we thought, we are discovering that the space we thought we were in is not fundamental and is akin to a hologram: like the shapes on the wall of Plato's cave, the world around us is produced by a more fundamental, dimensionally different, reality.

In my presentation, I will offer a quick introduction to some relevant aspects of string theory for philosophers without training in the subject to show how the approach can be used to mount metaphysical arguments. I will propose two arguments against the fundamentality of four-dimensional spacetime in relation to the idea of holography. In conclusion, I will describe several ways to metaphysically articulate the relation between this exotic ontology and the ordinary world.