Having introduced the necessary statistical technique, we are now in a position to establish routes from statistical mechanics to thermodynamics, i.e. to observable macroscopic properties. There are three such routes, provided by energy pressure (virial) compressibility equations of state. This brings us to a problem of thermodynamic consistency. As we will see later, all these equations require a knowledge of correlation functions. Since exact correlation functions for realistic potentials are not known and one has to use approximate models for them, an arbitrary thermodynamic property calculated on the basis of one equation of state will not in general be the same if calculated on the basis of another one. For example, the pressure calculated from the virial equation will differ from the pressure found by means of the compressibility equation.