In the third lecture, David Wallace asks how we make sense of probability in the Many-Worlds theory.

The Arrow of Time

The Many-Worlds Interpretation (MWI) of quantum mechanics holds that quantum theory - our best current theory of physics - is correctly understood as claiming that there are many worlds that exist in parallel to our own and which branch constantly off our own. The existence of the other worlds makes it possible to make sense of physics without action-at-a-distance, objective randomness, or any strange role for "observer" or "consciousness". During this weekend school we shall be discussing this interpretation of quantum mechanics and asking what would follow from its being the correct one.