The Feynman formulation of Quantum Mechanics builds three central ideas from the de Broglie hypothesis into the computation of quantum amplitudes: the probabilistic aspect of nature, superposition, and the classical limit. This is done by making the following three three postulates:
1. Events in nature are probabilistic with predictable probabilities P.
2. The probability P for an event to occur is given by the square of the complex magnitude of a quantum amplitude for the event, Q. The quantum amplitude Q associated with an event is the sum of the amplitudes associated with every history leading to the event.
3. The quantum amplitude associated with a given history is the product of the amplitudes associated with each fundamental process in the history.
This seems to contradict the very tools we use to perform the scientific method. Immediately after performing any experiment, the measurement becomes a historical event, and this says that we cannot say that any historical event has actually occurred. Thus, I cannot actually say that I performed an experiment and obtained a measurement....and if you cannot obtain concrete evidence, then you cannot prove scientific theories! In fact, if you cannot say that any past event has actually occurred, then you cannot use logic to describe the universe, because in logic a statement is true or false but cannot be "true with some probability"...and mathematics is derived from logic, so mathematics also breaks down!