The brute force computational approach will not resolve the
outstanding problems in disk galaxy formation. What seems to be
needed are further analytical insights that will allow
refinement of the simple prescriptions for star formation. One
such approach has come from studying turbulence-driven viscous
evolution of differentially rotating disks. Recent
investigations of star formation suggest that turbulence plays
an important role in accounting for the longevity of star-
forming clouds and their fragmentation into stars. The Jeans
mass in a typical interstellar cloud greatly exceeds the stellar
mass range. It is likely that the gravitational instability of
galaxy disks is a primary source of interstellar cloud turbulent
motions, supplemented on small scales by supernova feedback. Of
course, these drivers of turbulence are coupled together, since
the rates of star formation and star deaths are controlled by
global gravitational instability. In effect, differential
rotation is the ultimate source of the turbul