Bell's Three Options For Quantum Mechanics

John Bell showed that resolving the measurement problem leaves exactly three coherent options: (1) the wave function is not everything—add extra variables like particle positions (pilot-wave/Bohmian mechanics); (2) the wave function is not always right—it sometimes objectively collapses (GRW/objective-collapse, Penrose); or (3) keep only Schrodinger evolution with nothing besides the wave function, which forces the many-worlds branching picture.