The Hilbert space formulation is a central idea in quantum theory, but the ideas used by physicists to interpret the formulation widely differ. Furthermore, concepts in quantum mechanics are very abstract to those outside the field. Professor Inge Helland from the University of Oslo approaches these problems through what he calls ‘conceptual variables’, which belong to the minds of one or more conscious observers. From this basis, he achieves a new derivation of the Hilbert space formulation, which he hopes will lead to more satisfying studies of the foundations of quantum theory.