 Together, the two postulates induce the following reasoning. In every phenomenon the interaction between the object and the apparatus comprises at least one quantum. But the description of the phenomenon must use classical notions in which the quantum of action does not occur. Hence, the interaction cannot be analysed in this description. On the other hand, the classical character of the description allows us to speak in terms of the object itself. Instead of saying: “the interaction between a particle and a photographic plate has resulted in a black spot in a certain place on the plate”, we are allowed to forgo mentioning the apparatus and say: “the particle has been found in this place”. The experimental context, rather than changing or disturbing pre-existing properties of the object, defines what can meaningfully be said about the object.