In this paper we consider dissipative fluxes as well as the conserved variables as a set of independent variables characterizing the thermodynamic state of a nonequilibrium system. We then generalize the traditional internal energy balance equation so that contributions due to the dissipative fluxes are taken into consideration. On the other hand, the second law is formulated in terms of Caratheodory’s inaccessibility condition in conjunction with the assumption that dissipative energy associated with internal work arising from irreversible processes be semipositive definite. We show that the second law formulated in this manner is equivalent to Kelvin’s principle and Clausius’s principle, as well as Clausius’s inequality.