Quantum mechanics has engendered some philosophical disputes surrounding its conceptual foundation.To solve these disputes,some alternative interpretations which are different from orthodox(and Copenhagen) interpretation have been engendered.In the recent twenty years,the idea of decoherence has aroused attention among physicists and physical philosophers.Decoherence effects alone cannot solve the measurement problem.But decoherence including environmental interactions not only poses new conceptual questions but also suggests solutions to fundamental problems.
This paper develops a number of quantum mechanical characterisations of Stern-Gerlach. It discusses areas of vagueness in their formulation. Philosophers criticise quantum mechanics for unacceptable vagueness in connection with the measurement problem. The quantum formulation problems identified by this paper go beyond the locus of philosophical criticism. It concludes with an open question, are some areas of vagueness in quantum mechanics more acceptable philosophically than others and, if so, why?