  A phenomenological theory is presented for two-dimensional quantum liquids in
terms of the Fermi surface geometry. It is shown that there is a one-to-one
correspondence between the properties of an interacting electron system and its
corresponding Fermi surface. By doing this, the concept of Fermi surface is
generalized to include different topologies. It is shown that for a Fermi
liquid the corresponding Fermi surface is rough. In the presence of a
condensate, the Fermi surface is faceted, while for a ferromagnetc instability,
the Fermi surface becomes a frozen solid. I also determine the surface tension,
the step free energy, low lying excitations and other surface and transport
properties of the Fermi surface. The different transitions between these phases
are also determined. A non-Fermi liquid phase is shown to be a pre-roughening
state of the Fermi surface, the properties of which are briefly analyzed.
