ABSTRACT
As a matter of fact, no serious description of the Einstein-Podolsky-Rosen problem uses the incriminated postulate that the state vector is objective. The most straightforward case is that of realism. Realism, however, is not universally accepted. In Neil Bohr's philosophy, nonseparability is also present, but it has a very different meaning. The nonseparability of the quantum world is thus transferred, in this philosophy, from the system of the microparticles to the systems that each of these micro-objects constitutes with its instrument. In regard to Lorentz invariance, the transition from the pure case to the mixture—the reduction of the wave packet—raises less acute problems in Bohr's philosophy than it does in other approaches. Moreover, Bohr's philosophy obviously implies some restrictions on our freedom to imagine an independent external reality. The reason for this is that this conception endows the instruments with virtues that clearly transcend their status as mere physical systems —indeed, it ultimately defines instruments with reference to the desires.
