A new approach to teaching the principles of quantum mechanics is presented that leads quickly to the Hilbert space postulates. After convincing the reader that an algebra of observables is a useful way to describe probabilistic observations, the paper introduces an evolution operator and demonstrates that it cannot commute with position observables. This fact, plus elementary assumptions about the possible form of the evolution operator, are sufficient to demonstrate that, if the deterministic limit of the theory is to yield Newton’s law, the evolution operator must have the familiar form of the Hamiltonian: essentially kinetic energy plus potential energy.