Via kottke, here is a paper proposing A Unified Theory of Superman’s Powers.  The abstract reads as follows.

Since Time immemorial, man has sought to explain the powers of Kal-El, a.k.a. Superman. Siegel et al. Supposed that His mighty strength stems from His origin on another planet whose density and as a result, gravity, was much higher than our own. Natural selection on the planet of krypton would therefore endow Kal El with more efficient muscles and higher bone density; explaining, to first order, Superman’s extraordinary powers. Though concise, this theory has proved inaccurate. It is now clear that Superman is actually flying rather than just jumping really high; and His freeze-breath, x-ray vision, and heat vision also have no account in Seigel’s theory.

In this paper we propose a new unfied theory for the source of Superman’s powers; that is to say, all of Superman’s extraordinary powers are manifestation of one supernatural ability, rather than a host. It is our opinion that all of Superman’s recognized powers can be unified if His power is the ability to manipulate, from atomic to kilometer length scales, the inertia of His own and any matter with which He is in contact.

The paper goes on to show how the theory can explain Superman’s super strength, ability to fly, super senses, and even his heat vision and freeze breath.  It’s an elegant theory but the analysis has one significant gap.  It is not enough to find a simple principle from which all of Superman’s powers follow.   It is necessary to also show that the principle would not imply powers that Superman does not have.

If we do not insist on the latter, then there is an even simpler theory that does the trick:  Superman can do everything. (Although that comes with its own difficulties.)