I'm reading Enrico Fermi's "Thermodynamics" book. In page 3 of his book, he says: It is evident from what we have said that the knowledge of the thermodynamical state alone is by no means sufficient for the determination of the dynamical state. What does he mean by dynamical state? What's the difference between the thermodynamic state and the dynamical state? He then adds: Studying the thermodynamical state of a homogenous fluid of given volume at a given temperature (the pressure is then defined by the equation of state), we observe that there is an infinite number of states of molecular motion that correspond to it. With increasing time, the system exists succesively in all these dynamical states that correspond to the given thermodynamical state. From this point of view, we may say that a thermodynamical state is the ensemble of all the dynamical states through which, as a result of the molecular motion, the system is rapidly passing. Is he trying to say that there an infinite number of energy states given V, P and T? This paragraph just threw me off. Can someone explain the point he is trying to make in simpler words?