  Both also argued that the evolution toward equilibrium demanded in the non-equilibrium theory could also be understood probabilistically. Maxwell, introducing the notion of a “demon” who could manipulate the microscopic states of a system, argued that the law of entropic increase was only probabilistically valid. Boltzmann offered a probabilistic version of his equation describing the approach to equilibrium. Without considerable care, however, the Boltzmannian picture can still appear contrary to the objections from recurrence and reversibility interpreted in a probabilistic manner.