Filament Structure and Stability in the Solar Corona

We summarize and critically evaluate the basic theories for solar filaments and prominences presented up to date, as well as their stability. In particular we will discuss the role of the various current systems that may be present in determining equilibrium and stability properties, including those responsible for the torus instability and loss of equilibrium. We will then attempt to introduce some additional elements, such as the possible role of the longitudinal magnetic field evolution in the stability of prominences, as well as the consequences of their intrinsically dynamic nature.