This paper examines the underlying theory of structuralist growth models in an effort to compare that framework with the standard approach of Solow and others. Both the standard and structuralist models are solved in a common mathematical framework that emphasizes their similarities. It is seen that while the standard model requires the growth rate of the labor force to be taken as exogenously determined, the structuralist growth model must take investment growth to be determined exogenously in the long run. It is further seen that in order for the structuralist model to reliably converge to steady growth, considerable attention must be given to how agents make investment decisions. In many ways the standard model relies less on agency than does the structuralist. While the former requires a small number of plausible assumptions for steady growth to emerge, the structuralist model faces formidable challenges, especially if investment growth is thought to be determined by the rate of capacity utilization.