Preferred basis without decoherence

The aim of this paper is to argue that the "preferred basis problem" is not a real problem in measurement. We will show that, given an apparatus, among the infinite corrrelations that can be established in the final state by means of a change of basis, one and only one makes physical sense. It is the apparatus, through its interaction Hamiltonian, what selects a single basis and determines the observable to be measured, even without decoherence.