"Some theorists are led to supersymmetry because it emerges as part of the low energy theory from a superstring theory of everything. Others are particularly confident that nature will be supersymmetric because the Higgs mechanism is not an extra mechanism added ad hoc to the rest of the gauge theory, but emerges as a derived result (see the chapter by Ibáñez and Ross) if Mtop ≳ MW (which seems to be true). That is, supersymmetry can explain the ratio of the weak scale to the unification scale."