In 1929, in the wake of the enormous success of nonrelativistic quantum mechanics in explaining atomic and molecular structure and interactions, Dirac, one of the main contributor to these developments, in a now famous quotation asserted that "The general theory of quantum mechanics is now almost complete." Whatever imperfections still remained were connected with the synthesis of the theory with the special theory of relativity. But these were "... of no importance in the consideration of atomic and molecular structure and ordinary chemical reactions ... The underlying physical laws necessary for the mathematical theory of a large part of physics and the whole of chemistry are thus completely known, and the difficulty is only that exact application of these laws lead to equations much too complicated to be soluble ..."¹