Quantum theories of matter are astonishingly successful — and deeply mysterious.

Niels Bohr is said to have remarked that

"those who are not shocked when they first come across quantum theory cannot possibly have understood it."

Richard Feynman said

"I think I can safely say that nobody understands quantum mechanics."

Some quantum weirdness is unavoidable — it appears, for instance, that wholes really are more than the sum of their parts and that nature is non-local in a surprising way. Other weirdnesses are features of some ways of understanding quantum mechanics but not others: indeterminism, randomness, branching worlds, surprising connections between the physical and the mental. We will look at some currently popular approaches: Bohm's deterministic theory, spontaneous collapse theories, many-worlds and many-minds theories. Prior familiarity with quantum mechanics is not required (but comfort with algebra would be an asset).