Structure of Quantum Theory

In 1926, Max Born proposed that quantum theory (QT) arises from the "nonexistence of inner properties that determine a definite outcome," an idea that seems to have little explanatory power. However, we show that, by embedding this idea in the framework of general probabilistic theories (GPTs) and requiring that the theory's observables have outcomes that can be predicted with certainty without disturbance, one can derive the Hilbert space formalism of QT, including Born's rule. This approach unblocks the GPTs program for reconstructing quantum theory from physical principles, gives a second life to Einstein-Podolsky-Rosen (EPR) reasoning, and explains the sets of quantum correlations for all Bell and measurement contextuality scenarios, offering a unified resolution to long-standing foundational problems.