Event Detail

Tue Mar 12, 2024
Howison Library
4–6:15 PM
Townsend Visitor
Jenann Ismael (Johns Hopkins University)
Agency: Laplace Meets Gödel

Most day-to-day physics involves modelling other systems: cells, gases, fluids. In those contexts, we maintain a provisional separation of subject and object, or of investigator and system being investigated. When we are dealing with the universe as a whole, we are part of the subject matter, but we tend to adopt a god’s eye view, treating the universe imaginatively as though it were an object we were looking at the universe from the outside.

This is a convenient and mostly harmless fiction but it pushes out of view a phenomenon that I’m going to call interference. Interference arises because we are part of the universe. That means that our representational activity is connected in the domain that we are representing and it is going to be impossible to stabilize some facts or events in the world independently of the act of representing them. This fact turns out to be important in some philosophically contested contexts. I’ll be exploring its fallout.

Lecture 2 – Agency: Laplace Meets Gödel

Classical mechanics – our clearest and best understood example of a deterministic theory - entails that a being that knew the initial conditions of the universe would be able to predict everything that happens. Laplace gave us the image of a demon that knows the positions and momenta of all the particles of which the universe is composed and as he says ‘embraces in a single formula’ everything that will ever happen. I’ll argue that there are both specific and general reasons that there could not be a Laplacian demon in the world: not for classical physics, not for any theory.

The general reasons have to do with the fact that such a demon – if it existed – would be able to truthfully answer every yes/no question of physical fact. But there is a Master Argument against this existence of such a thing: we can always find a question such a demon can’t answer (“is the answer to the question that is about to appear in the output channel ‘no’. I’ll look at what that means for determinism and for some of the philosophical lessons that it has been used to support.