 Bohr’s central insight was that if a measuring instrument is to serve its purpose of furnishing us with knowledge of an object – that is to say, if it is to be described functionally – it must be described classically. Of course, it is always possible to represent the experimental apparatus from a purely structural point of view as a quantum-mechanical system without any reference to its function. However, any functional description of the experimental apparatus, in which it is treated as a means to an end, and not merely as a dynamical system, must make use of the concepts of classical physics (Camilleri, 2017, pp.30–31).