of probabilities, and are satisfied if , where is a unitary matrix. Postulate 3 If and are two complete questions, then the unitary matrix associated with their probability described above satisfies the equality , for all and . This third postulate implies that if we set a complete question as a basis vector in a complex Hilbert space, we may then represent any other question as a linear combination: And the conventional probability rule of quantum mechanics states that if two sets of basis vectors are in the relation above, then the probability is Dynamics The Heisenberg picture of time evolution accords most easily with RQM. Questions may be labelled by a time parameter , and are regarded as distinct if they are specified by the same operator but are performed at different times. Because time evolution is a symmetry in the theory (it forms a necessary part of the full formal derivation of the theory from the postulates), the set of all possible questions at time is isomorphic to the set of all possible questions at time . It follows, by standard arguments in quantum logic, from the derivation above that the orthomodular lattice has the structure of the set of linear subspaces of a Hilbert space, with the relations between the questions corresponding to the relations between linear subspaces. It follows that there must be a unitary transformation that satisfies: and where is the Hamiltonian, a self-adjoint operator on the Hilbert space and the unitary matrices are an abelian group. Problems and discussion The question is whether RQM denies any objective reality, or otherwise stated: there is only a subjectively knowable reality. Rovelli limits the scope of this claim by stating that RQM relates to the variables of a physical system and not to constant, intrinsic properties, such as the mass and charge of an electron. Indeed, mechanics in general only predicts the behavior of a physical system under various conditions. In classical mechanics this behavior is mathematically represented in a phase space with certain degrees of freedom; in quantum mechanics this is a state space, mathematically represented as a multidimensional complex Hilbert space, in which the dimensions correspond to the above variables. Dorato, however, argues that all intrinsic properties of a physical system, including mass and charge, are only knowable in a subjective interaction between the observer and the physical system. The unspoken thought behind this is