Self-regulation of star formation in disks is controlled by two dimensionless parameters: the Toomre parameter for gravitational instability and the porosity of the interstellar medium to supernova remnant–heated gas. An interplay between these leads to expressions for the gas velocity dispersion, gas fraction, star formation rate and star formation efficiency in disks and to a possible explanation of the Tully-Fisher relation. I further develop feedback arguments that arise from the impact of massive star formation and death on protogalaxies in order to account for the characteristic luminosity of a galaxy and for early winds from forming spheroids.