Independent results from experiment and computer simulations, pertaining to the change in physical properties of glass-forming liquids throughout the transition range, have been examined in the context of a two-state model. The complex mechanical moduli for a number of glass-forming oxides have been determined as a function of the temperature, using Brillouin light scattering. The temperature dependence of these moduli, which is characterized by the lack of thermo-theological simplicity, can be adequately and consistently described by a two-state model. The relaxational modulus can be attributed solely to a peculiar viscoelastic structural state, which gradually comes into existence at high temperatures, as a result of structural transitions from the glassy to the viscoelastic state. The temperature dependence of inherent structure energies, as obtained by computer simulations of a Lennard-Jones fluid, by Sastry et al., can be described with the same two-state model. The ubiquitous behavior in these independent findings provides support for the concept that thermodynamically driven structural transitions underlie the glass transition.