 is often thought of as the basic dynamical law of quantum mechanics, where \(H\) (called the Hamiltonian operator) is said to represent the system’s energy. Instead QBists take this equation as providing a synchronic constraint on an agent’s credences concerning the agent‘s experiences at different times, and not a diachronic constraint on the system’s properties at those times. QBists also consider the Hamiltonian (along with all other observables) within the purview of each individual agent rather than objectively determined by the system’s properties. It follows that equally rational agents who assign the same quantum state to a system at a time \(t_1\) may consistently assign it different states at a time \(t_2\) because they apply the constraint supplied by the Schrödinger equation in different ways.