When Physicists speak of "beauty" in their theories, they really mean that their theory possesses at least… — Michio Kaku

Maxwell's equations... originally consisted of eight equations. These equations are not "beautiful." They do not possess much symmetry. In their original form, they are ugly. ...However, when rewritten using time as the fourth dimension, this rather awkward set of eight equations collapses into a single tensor equation. This is what a physicist calls "beauty," because both criteria are now satisfied.

Remarkably, only a handful of fundamental physical principles are sufficient to summarize most of modern physics.

No other theory known to science [other than superstring theory] uses such powerful mathematics at such a fundamental level. ...because any unified field theory first must absorb the Riemannian geometry of Einstein's theory and the Lie groups coming from quantum field theory... The new mathematics, which is responsible for the merger of these two theories, is topology, and it is responsible for accomplishing the seemingly impossible task of abolishing the infinities of a quantum theory of gravity.