Quantum mechanics is perhaps the greatest scientific puzzle of all time. It is spectacularly successful in explaining many aspects of the world, yet people give wildly conflicting accounts of what it is about. The basic issue is that the dynamics of the theory is deterministic, yet probability is supposed to play a role. This series of two talks surveys various attempts to uncover some kind of reality underlying quantum mechanics. It is purely expository and will only deal with non-relativistic quantum mechanics.

The first talk will deal with approaches in which the relevant random quantities emerge as the result of ``measurement.'' This presupposes that there is an account of ``measurement'' that is internal to quantum mechanics.

The second talk will deal with accounts where the random quantities do not depend on ``measurement'' or where there is no randomness at all.