 Much of contemporary theoretical research in chemistry involves the application of quantum mechanics to chemistry. While exact solutions to the quantum mechanical descriptions of chemical phenomena have not been achieved, advances in theoretical physics, applied mathematics, and computation have made it possible to calculate the chemical properties of many molecules very accurately and with few idealizations. The approach of striving for ever more accurate calculations with decreasing levels of idealization is endorsed by many quantum chemists. For example, the development team of Gaussian, one of the leading packages for doing quantum chemical calculations, explicitly endorses this position. While they admit that there are many considerations that enter into the choice of the degree of approximation or “level of theory” for any calculation, the goal is to de-idealize the models as much as possible. They argue that quantum chemical calculations which are arbitrarily close to the exact solutions are the “limit to which all approximate methods strive” (Foresman &amp; Frisch 1996).