] 2 6 A pr 1 99 9 Supersymmetry : A new organizing principle for the microworld ? ∗

A glorious achievement of twentieth century Physics is the identification of the building blocks of nature. A related triumph a deep understanding of the forces of interaction. In particular, it has been possible to understand the four fundamental forces of nature in an elegant and unified mathematical framework. The paradigm for this unification has been the principle of gauge symmetry. A new approach to achieving further unification relies on Supersymmetry. This is a symmetry which relates particles of integer spin with those of half-integral spin and also dictates the allowed interactions among these particles. However, no data exist pointing to the presence of this symmetry; it may indeed be of no relevance to nature. In this paper the gauge principle and unification attempts are briefly reviewed, and then Supersymmetry is introduced. The notion of “broken” symmetry is discussed, which may explain why the symmetry is difficult to observe at presently accessible energies. But a badly broken manifestation seems to remove much of the original appeal and elegance of the theory. We here propose two alternative views of the status of Supersymmetry from fundamental standpoint. There is a good reason why it is indeed a fundamental symmetry, despite badly broken. The alternative is that it is an organizing principle, somewhat like valence. This makes it valuable as a signpost to new Physics.