The success of the standard model in explaining low energy (≈ 100GeV) physics within the framework of spontaneously broken Yang-Mills theory has given physicists the hope that the Einstein dream of a unified theory of fundamental interactions might be achieved using geometrical methods of local symmetry principles supplemented by consistency requirements such as renormalization, unitarity and, most crucially, compatibility with present low energy data.Merging these principles with the quantum-mechanical notions of spin and statistics led physicists further to develop new theories in the...