state by a measurement. Indeed, having many similar quantum systems prepared in identical ways and subjecting each one to identical measurements, one will obtain a collection of measurement values from among a common (often discrete) set that only depends on the setup and the instrument, called the *eigenvalues* of the observable in question (as mentioned in the previous section, the observable itself being defined by the instrument). The distribution of *probabilities of occurrence* of eigenvalues (including the latter’s mean value and standard deviation) is what characterizes the common state of each quantum system of the set at the time of measurement (Born’s Rule). While it is impossible to predict the outcome of the measurement of any *one* system, the set of probabilities of obtaining the eigenvalues is deterministic in the sense that it depends only on the preparation and history of the quantum system and on the apparatus used.[^12] This is not all: when a single quantum system is measured and one of the possible eigenvalues of the corresponding observable is obtained, that quantum system emerges in a special state such that a repeated measurement of the exactly same kind immediately thereafter will always yield the same eigenvalue.[^13] Such a 