Quantum-mechanical self-measurement

The idea of self-measurement by a quantum-mechancal automaton is presented, and the conclusions that are typically reached about what we can come to know from doing self-measurements are shown to be mistaken. Specifically, it is shown that, while we are capable of predicting and measuring the values of two incompatible observables, we are incapable of knowing both these values simultaneously. This is an example of the interesting limitations quantum mechanics places on knowledge.