  Recall (section 5.3) that in no-collapse theories, quantum-mechanical states always evolve according to a unitary and linear equation of motion (the Schrödinger equation in the non-relativistic case), and accordingly they never collapse. Since the wave function has a covariant dynamics, the question of the compatibility with relativity turns on the dynamics of the additional properties —the so-called ‘hidden variables’— that no-collapse theories typically postulate. In Albert and Loewer's many-minds theory (see section 5.3.3), the wave function has covariant dynamics, and no additional physical properties are postulated. Accordingly, the theory is genuinely relativistic. Yet, as the compatibility with relativity is achieved at the cost of postulating that outcomes of measurements (and, typically, any other perceived properties) are mental rather than physical properties, many find this way of reconciling quantum mechanics with relativity unsatisfactory. 